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	$50.74	5.873%	$53.72	$53.72	$53.70	$53.70
Purchase #2	$12.42	10.776%	$13.7584	$13.76	$13.75	$13.80
Purchase #3	$128.40	10.246%	$141.5559	$141.56	$141.55	$141.60
Purchase #4	$247.38	13.518%	$280.8208	$280.82	$280.80	$280.80
Purchase #5	$191.42	10.633%	$211.7737	$211.77	$211.75	$211.80
Purchase #6	$230.54	8.272%	$249.6103	$249.61	$249.60	$249.60
Purchase #7	$118.61	6.677%	$126.5296	$126.53	$126.55	$126.50
7 purchase totals =	$979.51		$1,077.7687	$1,077.77	$1,077.70	$1,077.80