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	$118.92	11.122%	$132.1463	$132.15	$132.15	$132.10
Purchase #2	$220.30	8.358%	$238.7127	$238.71	$238.70	$238.70
Purchase #3	$89.38	5.480%	$94.278	$94.28	$94.30	$94.30
Purchase #4	$144.61	6.251%	$153.6496	$153.65	$153.65	$153.60
Purchase #5	$77.44	6.305%	$82.3226	$82.32	$82.30	$82.30
Purchase #6	$223.75	9.263%	$244.476	$244.48	$244.50	$244.50
Purchase #7	$65.94	12.387%	$74.108	$74.11	$74.10	$74.10
7 purchase totals =	$940.34		$1,019.6932	$1,019.70	$1,019.70	$1,019.60