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	$61.42	3.366%	$63.4874	$63.49	$63.50	$63.50
Purchase #2	$211.46	5.659%	$223.4265	$223.43	$223.45	$223.40
Purchase #3	$70.39	11.591%	$78.5489	$78.55	$78.55	$78.50
Purchase #4	$148.65	3.644%	$154.0668	$154.07	$154.05	$154.10
Purchase #5	$131.76	7.267%	$141.335	$141.34	$141.35	$141.30
Purchase #6	$243.44	3.300%	$251.4735	$251.47	$251.45	$251.50
Purchase #7	$114.80	5.809%	$121.4687	$121.47	$121.45	$121.50
7 purchase totals =	$981.92		$1,033.8068	$1,033.82	$1,033.80	$1,033.80