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	$44.71	13.523%	$50.7561	$50.76	$50.75	$50.80
Purchase #2	$42.48	6.112%	$45.0764	$45.08	$45.10	$45.10
Purchase #3	$233.51	5.362%	$246.0308	$246.03	$246.05	$246.00
Purchase #4	$212.89	5.154%	$223.8624	$223.86	$223.85	$223.90
Purchase #5	$49.93	8.826%	$54.3368	$54.34	$54.35	$54.30
Purchase #6	$164.58	12.711%	$185.4998	$185.50	$185.50	$185.50
Purchase #7	$207.91	8.173%	$224.9025	$224.90	$224.90	$224.90
7 purchase totals =	$956.01		$1,030.4648	$1,030.47	$1,030.50	$1,030.50