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	$60.76	6.223%	$64.5411	$64.54	$64.55	$64.50
Purchase #2	$52.66	10.199%	$58.0308	$58.03	$58.05	$58.00
Purchase #3	$79.36	13.175%	$89.8157	$89.82	$89.80	$89.80
Purchase #4	$76.69	3.393%	$79.2921	$79.29	$79.30	$79.30
Purchase #5	$89.86	7.333%	$96.4494	$96.45	$96.45	$96.40
Purchase #6	$35.63	13.711%	$40.5152	$40.52	$40.50	$40.50
Purchase #7	$50.92	5.343%	$53.6407	$53.64	$53.65	$53.60
7 purchase totals =	$445.88		$482.2850	$482.29	$482.30	$482.10