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	$235.61	12.809%	$265.7893	$265.79	$265.80	$265.80
Purchase #2	$50.51	8.418%	$54.7619	$54.76	$54.75	$54.80
Purchase #3	$236.50	8.437%	$256.4535	$256.45	$256.45	$256.50
Purchase #4	$29.53	6.364%	$31.4093	$31.41	$31.40	$31.40
Purchase #5	$48.59	7.824%	$52.3917	$52.39	$52.40	$52.40
Purchase #6	$126.82	8.426%	$137.5059	$137.51	$137.50	$137.50
Purchase #7	$234.63	7.297%	$251.751	$251.75	$251.75	$251.80
7 purchase totals =	$962.19		$1,050.0626	$1,050.06	$1,050.05	$1,050.20