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	$172.72	13.630%	$196.2617	$196.26	$196.25	$196.30
Purchase #2	$198.28	12.508%	$223.0809	$223.08	$223.10	$223.10
Purchase #3	$224.76	8.368%	$243.5679	$243.57	$243.55	$243.60
Purchase #4	$30.84	6.123%	$32.7283	$32.73	$32.75	$32.70
Purchase #5	$124.35	10.639%	$137.5796	$137.58	$137.60	$137.60
Purchase #6	$128.72	5.604%	$135.9335	$135.93	$135.95	$135.90
Purchase #7	$185.30	4.327%	$193.3179	$193.32	$193.30	$193.30
7 purchase totals =	$1,064.97		$1,162.4698	$1,162.47	$1,162.50	$1,162.50