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	$109.89	8.169%	$118.8669	$118.87	$118.85	$118.90
Purchase #2	$48.87	13.161%	$55.3018	$55.30	$55.30	$55.30
Purchase #3	$88.45	13.517%	$100.4058	$100.41	$100.40	$100.40
Purchase #4	$152.39	4.513%	$159.2674	$159.27	$159.25	$159.30
Purchase #5	$108.79	8.781%	$118.3428	$118.34	$118.35	$118.30
Purchase #6	$57.31	11.817%	$64.0823	$64.08	$64.10	$64.10
Purchase #7	$184.28	6.362%	$196.0039	$196.00	$196.00	$196.00
7 purchase totals =	$749.98		$812.2709	$812.27	$812.25	$812.30