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	$91.66	12.872%	$103.4585	$103.46	$103.45	$103.50
Purchase #2	$195.32	11.432%	$217.649	$217.65	$217.65	$217.60
Purchase #3	$108.82	10.375%	$120.1101	$120.11	$120.10	$120.10
Purchase #4	$150.42	3.107%	$155.0935	$155.09	$155.10	$155.10
Purchase #5	$99.61	3.548%	$103.1442	$103.14	$103.15	$103.10
Purchase #6	$211.52	7.618%	$227.6336	$227.63	$227.65	$227.60
Purchase #7	$52.54	9.705%	$57.639	$57.64	$57.65	$57.60
7 purchase totals =	$909.89		$984.7279	$984.72	$984.75	$984.60