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	$42.45	6.630%	$45.2644	$45.26	$45.25	$45.30
Purchase #2	$151.52	11.572%	$169.0539	$169.05	$169.05	$169.10
Purchase #3	$248.39	8.359%	$269.1529	$269.15	$269.15	$269.20
Purchase #4	$219.37	12.282%	$246.313	$246.31	$246.30	$246.30
Purchase #5	$29.31	11.254%	$32.6085	$32.61	$32.60	$32.60
Purchase #6	$185.36	13.810%	$210.9582	$210.96	$210.95	$211.00
Purchase #7	$57.45	3.459%	$59.4372	$59.44	$59.45	$59.40
7 purchase totals =	$933.85		$1,032.7881	$1,032.78	$1,032.75	$1,032.90