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	$72.39	7.663%	$77.9372	$77.94	$77.95	$77.90
Purchase #2	$140.93	4.137%	$146.7603	$146.76	$146.75	$146.80
Purchase #3	$99.47	3.639%	$103.0897	$103.09	$103.10	$103.10
Purchase #4	$38.45	12.601%	$43.2951	$43.30	$43.30	$43.30
Purchase #5	$242.71	11.437%	$270.4687	$270.47	$270.45	$270.50
Purchase #6	$40.77	12.256%	$45.7668	$45.77	$45.75	$45.80
Purchase #7	$240.97	6.567%	$256.7945	$256.79	$256.80	$256.80
7 purchase totals =	$875.69		$944.1123	$944.12	$944.10	$944.20