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	$209.90	9.169%	$229.1457	$229.15	$229.15	$229.10
Purchase #2	$46.60	12.303%	$52.3332	$52.33	$52.35	$52.30
Purchase #3	$148.45	4.790%	$155.5608	$155.56	$155.55	$155.60
Purchase #4	$35.72	3.564%	$36.9931	$36.99	$37.00	$37.00
Purchase #5	$228.38	5.647%	$241.2766	$241.28	$241.30	$241.30
Purchase #6	$214.33	3.801%	$222.4767	$222.48	$222.50	$222.50
Purchase #7	$55.51	6.447%	$59.0887	$59.09	$59.10	$59.10
7 purchase totals =	$938.89		$996.8748	$996.88	$996.95	$996.90