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	$173.95	6.421%	$185.1193	$185.12	$185.10	$185.10
Purchase #2	$226.79	11.772%	$253.4877	$253.49	$253.50	$253.50
Purchase #3	$44.59	9.699%	$48.9148	$48.91	$48.90	$48.90
Purchase #4	$208.31	4.862%	$218.438	$218.44	$218.45	$218.40
Purchase #5	$105.64	13.791%	$120.2088	$120.21	$120.20	$120.20
Purchase #6	$126.38	4.379%	$131.9142	$131.91	$131.90	$131.90
Purchase #7	$233.38	7.328%	$250.4821	$250.48	$250.50	$250.50
7 purchase totals =	$1,119.04		$1,208.5649	$1,208.56	$1,208.55	$1,208.50