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	$93.52	3.233%	$96.5435	$96.54	$96.55	$96.50
Purchase #2	$88.26	13.590%	$100.2545	$100.25	$100.25	$100.30
Purchase #3	$62.39	6.257%	$66.2937	$66.29	$66.30	$66.30
Purchase #4	$244.96	10.687%	$271.1389	$271.14	$271.15	$271.10
Purchase #5	$37.82	10.717%	$41.8732	$41.87	$41.85	$41.90
Purchase #6	$221.39	9.720%	$242.9091	$242.91	$242.90	$242.90
Purchase #7	$106.63	13.608%	$121.1402	$121.14	$121.15	$121.10
7 purchase totals =	$854.97		$940.1531	$940.14	$940.15	$940.10