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	$167.33	10.810%	$185.4184	$185.42	$185.40	$185.40
Purchase #2	$74.73	11.691%	$83.4667	$83.47	$83.45	$83.50
Purchase #3	$200.49	7.860%	$216.2485	$216.25	$216.25	$216.20
Purchase #4	$106.48	12.236%	$119.5089	$119.51	$119.50	$119.50
Purchase #5	$97.84	13.663%	$111.2079	$111.21	$111.20	$111.20
Purchase #6	$155.46	13.207%	$175.9916	$175.99	$176.00	$176.00
Purchase #7	$71.86	6.688%	$76.666	$76.67	$76.65	$76.70
7 purchase totals =	$874.19		$968.5080	$968.52	$968.45	$968.50