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	$44.95	4.309%	$46.8869	$46.89	$46.90	$46.90
Purchase #2	$120.52	13.693%	$137.0228	$137.02	$137.00	$137.00
Purchase #3	$33.47	7.197%	$35.8788	$35.88	$35.90	$35.90
Purchase #4	$5.69	4.409%	$5.9409	$5.94	$5.95	$5.90
Purchase #5	$194.48	11.111%	$216.0887	$216.09	$216.10	$216.10
Purchase #6	$146.76	3.412%	$151.7675	$151.77	$151.75	$151.80
Purchase #7	$94.99	9.162%	$103.693	$103.69	$103.70	$103.70
7 purchase totals =	$640.86		$697.2786	$697.28	$697.30	$697.30