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	$215.90	13.750%	$245.5863	$245.59	$245.60	$245.60
Purchase #2	$194.76	3.594%	$201.7597	$201.76	$201.75	$201.80
Purchase #3	$212.45	13.604%	$241.3517	$241.35	$241.35	$241.40
Purchase #4	$92.67	11.168%	$103.0194	$103.02	$103.00	$103.00
Purchase #5	$96.86	13.479%	$109.9158	$109.92	$109.90	$109.90
Purchase #6	$7.33	4.570%	$7.665	$7.67	$7.65	$7.70
Purchase #7	$89.41	4.618%	$93.539	$93.54	$93.55	$93.50
7 purchase totals =	$909.38		$1,002.8369	$1,002.85	$1,002.80	$1,002.90