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	$193.56	3.650%	$200.6249	$200.62	$200.60	$200.60
Purchase #2	$133.89	7.329%	$143.7028	$143.70	$143.70	$143.70
Purchase #3	$244.70	8.607%	$265.7613	$265.76	$265.75	$265.80
Purchase #4	$175.70	4.501%	$183.6083	$183.61	$183.60	$183.60
Purchase #5	$24.33	12.260%	$27.3129	$27.31	$27.30	$27.30
Purchase #6	$86.91	3.720%	$90.1431	$90.14	$90.15	$90.10
Purchase #7	$184.58	4.385%	$192.6738	$192.67	$192.65	$192.70
7 purchase totals =	$1,043.67		$1,103.8271	$1,103.81	$1,103.75	$1,103.80