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	$59.98	9.222%	$65.5114	$65.51	$65.50	$65.50
Purchase #2	$185.96	10.207%	$204.9409	$204.94	$204.95	$204.90
Purchase #3	$66.39	5.659%	$70.147	$70.15	$70.15	$70.10
Purchase #4	$74.75	9.720%	$82.0157	$82.02	$82.00	$82.00
Purchase #5	$168.65	10.132%	$185.7376	$185.74	$185.75	$185.70
Purchase #6	$106.41	11.181%	$118.3077	$118.31	$118.30	$118.30
Purchase #7	$93.70	6.838%	$100.1072	$100.11	$100.10	$100.10
7 purchase totals =	$755.84		$826.7675	$826.78	$826.75	$826.60