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	$134.73	10.426%	$148.7769	$148.78	$148.80	$148.80
Purchase #2	$227.93	13.532%	$258.7735	$258.77	$258.75	$258.80
Purchase #3	$206.31	11.576%	$230.1924	$230.19	$230.20	$230.20
Purchase #4	$27.46	5.224%	$28.8945	$28.89	$28.90	$28.90
Purchase #5	$101.43	4.637%	$106.1333	$106.13	$106.15	$106.10
Purchase #6	$143.80	7.745%	$154.9373	$154.94	$154.95	$154.90
Purchase #7	$153.32	12.444%	$172.3991	$172.40	$172.40	$172.40
7 purchase totals =	$994.98		$1,100.1070	$1,100.10	$1,100.15	$1,100.10