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	$198.34	4.222%	$206.7139	$206.71	$206.70	$206.70
Purchase #2	$200.70	11.254%	$223.2868	$223.29	$223.30	$223.30
Purchase #3	$144.66	11.241%	$160.9212	$160.92	$160.90	$160.90
Purchase #4	$78.35	13.364%	$88.8207	$88.82	$88.80	$88.80
Purchase #5	$154.29	5.204%	$162.3193	$162.32	$162.30	$162.30
Purchase #6	$208.92	6.743%	$223.0075	$223.01	$223.00	$223.00
Purchase #7	$236.72	11.421%	$263.7558	$263.76	$263.75	$263.80
7 purchase totals =	$1,221.98		$1,328.8252	$1,328.83	$1,328.75	$1,328.80