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	$33.67	11.293%	$37.4724	$37.47	$37.45	$37.50
Purchase #2	$157.86	13.539%	$179.2327	$179.23	$179.25	$179.20
Purchase #3	$137.75	4.250%	$143.6044	$143.60	$143.60	$143.60
Purchase #4	$194.73	7.451%	$209.2393	$209.24	$209.25	$209.20
Purchase #5	$86.75	13.162%	$98.168	$98.17	$98.15	$98.20
Purchase #6	$211.96	10.844%	$234.9449	$234.94	$234.95	$234.90
Purchase #7	$130.83	10.377%	$144.4062	$144.41	$144.40	$144.40
7 purchase totals =	$953.55		$1,047.0679	$1,047.06	$1,047.05	$1,047.00