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	$48.83	7.470%	$52.4776	$52.48	$52.50	$52.50
Purchase #2	$192.89	13.724%	$219.3622	$219.36	$219.35	$219.40
Purchase #3	$243.33	7.632%	$261.9009	$261.90	$261.90	$261.90
Purchase #4	$191.88	8.520%	$208.2282	$208.23	$208.25	$208.20
Purchase #5	$206.76	11.152%	$229.8179	$229.82	$229.80	$229.80
Purchase #6	$57.25	12.554%	$64.4372	$64.44	$64.45	$64.40
Purchase #7	$27.38	4.471%	$28.6042	$28.60	$28.60	$28.60
7 purchase totals =	$968.32		$1,064.8282	$1,064.83	$1,064.85	$1,064.80