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	$40.61	7.130%	$43.5055	$43.51	$43.50	$43.50
Purchase #2	$141.57	6.338%	$150.5427	$150.54	$150.55	$150.50
Purchase #3	$201.43	9.640%	$220.8479	$220.85	$220.85	$220.80
Purchase #4	$199.77	5.780%	$211.3167	$211.32	$211.30	$211.30
Purchase #5	$161.47	7.865%	$174.1696	$174.17	$174.15	$174.20
Purchase #6	$71.76	6.798%	$76.6382	$76.64	$76.65	$76.60
Purchase #7	$142.65	5.352%	$150.2846	$150.28	$150.30	$150.30
7 purchase totals =	$959.26		$1,027.3052	$1,027.31	$1,027.30	$1,027.20