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	$70.63	11.244%	$78.5716	$78.57	$78.55	$78.60
Purchase #2	$42.47	6.859%	$45.383	$45.38	$45.40	$45.40
Purchase #3	$175.98	5.566%	$185.775	$185.78	$185.80	$185.80
Purchase #4	$207.94	11.143%	$231.1108	$231.11	$231.10	$231.10
Purchase #5	$48.94	7.333%	$52.5288	$52.53	$52.55	$52.50
Purchase #6	$130.63	10.757%	$144.6819	$144.68	$144.70	$144.70
Purchase #7	$188.42	6.124%	$199.9588	$199.96	$199.95	$200.00
7 purchase totals =	$865.01		$938.0099	$938.01	$938.05	$938.10