Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$196.40	12.211%	$220.3824	$220.38	$220.40	$220.40
Purchase #2	$165.91	13.825%	$188.8471	$188.85	$188.85	$188.80
Purchase #3	$179.73	6.197%	$190.8679	$190.87	$190.85	$190.90
Purchase #4	$170.36	10.273%	$187.8611	$187.86	$187.85	$187.90
Purchase #5	$146.37	6.143%	$155.3615	$155.36	$155.35	$155.40
Purchase #6	$122.98	3.526%	$127.3163	$127.32	$127.30	$127.30
Purchase #7	$184.55	10.627%	$204.1621	$204.16	$204.15	$204.20
7 purchase totals =	$1,166.30		$1,274.7984	$1,274.80	$1,274.75	$1,274.90