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	$154.52	11.817%	$172.7796	$172.78	$172.80	$172.80
Purchase #2	$35.41	13.291%	$40.1163	$40.12	$40.10	$40.10
Purchase #3	$89.79	8.200%	$97.1528	$97.15	$97.15	$97.20
Purchase #4	$46.80	10.590%	$51.7561	$51.76	$51.75	$51.80
Purchase #5	$126.72	3.185%	$130.756	$130.76	$130.75	$130.80
Purchase #6	$194.63	3.182%	$200.8231	$200.82	$200.80	$200.80
Purchase #7	$75.72	4.628%	$79.2243	$79.22	$79.20	$79.20
7 purchase totals =	$723.59		$772.6082	$772.61	$772.55	$772.70