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	$172.93	9.560%	$189.4621	$189.46	$189.45	$189.50
Purchase #2	$43.79	9.755%	$48.0617	$48.06	$48.05	$48.10
Purchase #3	$216.25	10.393%	$238.7249	$238.72	$238.70	$238.70
Purchase #4	$103.83	7.138%	$111.2414	$111.24	$111.25	$111.20
Purchase #5	$246.84	11.664%	$275.6314	$275.63	$275.65	$275.60
Purchase #6	$157.74	11.841%	$176.418	$176.42	$176.40	$176.40
Purchase #7	$156.57	7.290%	$167.984	$167.98	$168.00	$168.00
7 purchase totals =	$1,097.95		$1,207.5235	$1,207.51	$1,207.50	$1,207.50