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	$53.56	3.699%	$55.5412	$55.54	$55.55	$55.50
Purchase #2	$59.39	12.374%	$66.7389	$66.74	$66.75	$66.70
Purchase #3	$219.61	4.386%	$229.2421	$229.24	$229.25	$229.20
Purchase #4	$57.69	8.376%	$62.5221	$62.52	$62.50	$62.50
Purchase #5	$242.38	13.257%	$274.5123	$274.51	$274.50	$274.50
Purchase #6	$135.63	13.717%	$154.2344	$154.23	$154.25	$154.20
Purchase #7	$137.40	5.412%	$144.8361	$144.84	$144.85	$144.80
7 purchase totals =	$905.66		$987.6271	$987.62	$987.65	$987.40