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	$175.63	13.573%	$199.4683	$199.47	$199.45	$199.50
Purchase #2	$185.25	13.422%	$210.1143	$210.11	$210.10	$210.10
Purchase #3	$76.92	11.121%	$85.4743	$85.47	$85.45	$85.50
Purchase #4	$118.73	4.323%	$123.8627	$123.86	$123.85	$123.90
Purchase #5	$149.72	8.650%	$162.6708	$162.67	$162.65	$162.70
Purchase #6	$114.49	13.652%	$130.1202	$130.12	$130.10	$130.10
Purchase #7	$115.37	11.167%	$128.2534	$128.25	$128.25	$128.30
7 purchase totals =	$936.11		$1,039.9640	$1,039.95	$1,039.85	$1,040.10