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	$60.74	7.200%	$65.1133	$65.11	$65.10	$65.10
Purchase #2	$56.95	4.479%	$59.5008	$59.50	$59.50	$59.50
Purchase #3	$58.96	3.663%	$61.1197	$61.12	$61.10	$61.10
Purchase #4	$95.26	7.280%	$102.1949	$102.19	$102.20	$102.20
Purchase #5	$55.84	10.620%	$61.7702	$61.77	$61.75	$61.80
Purchase #6	$196.69	13.543%	$223.3277	$223.33	$223.35	$223.30
Purchase #7	$141.61	9.296%	$154.7741	$154.77	$154.75	$154.80
7 purchase totals =	$666.05		$727.8007	$727.79	$727.75	$727.80