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	$166.75	4.112%	$173.6068	$173.61	$173.60	$173.60
Purchase #2	$100.34	5.582%	$105.941	$105.94	$105.95	$105.90
Purchase #3	$230.41	7.558%	$247.8244	$247.82	$247.80	$247.80
Purchase #4	$89.78	5.744%	$94.937	$94.94	$94.95	$94.90
Purchase #5	$181.89	13.701%	$206.8107	$206.81	$206.80	$206.80
Purchase #6	$53.80	12.839%	$60.7074	$60.71	$60.70	$60.70
Purchase #7	$192.89	7.170%	$206.7202	$206.72	$206.70	$206.70
7 purchase totals =	$1,015.86		$1,096.5475	$1,096.55	$1,096.50	$1,096.40