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	$146.55	9.411%	$160.3418	$160.34	$160.35	$160.30
Purchase #2	$123.40	5.662%	$130.3869	$130.39	$130.40	$130.40
Purchase #3	$233.62	8.731%	$254.0174	$254.02	$254.00	$254.00
Purchase #4	$91.59	8.620%	$99.4851	$99.49	$99.50	$99.50
Purchase #5	$54.86	9.530%	$60.0882	$60.09	$60.10	$60.10
Purchase #6	$147.57	13.659%	$167.7266	$167.73	$167.75	$167.70
Purchase #7	$59.71	9.511%	$65.389	$65.39	$65.40	$65.40
7 purchase totals =	$857.30		$937.4350	$937.45	$937.50	$937.40