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	$161.47	4.299%	$168.4116	$168.41	$168.40	$168.40
Purchase #2	$32.47	8.288%	$35.1611	$35.16	$35.15	$35.20
Purchase #3	$62.97	13.386%	$71.3992	$71.40	$71.40	$71.40
Purchase #4	$27.62	3.327%	$28.5389	$28.54	$28.55	$28.50
Purchase #5	$111.82	12.449%	$125.7405	$125.74	$125.75	$125.70
Purchase #6	$208.98	6.302%	$222.1499	$222.15	$222.15	$222.10
Purchase #7	$92.40	8.120%	$99.9029	$99.90	$99.90	$99.90
7 purchase totals =	$697.73		$751.3041	$751.30	$751.30	$751.20