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	$154.80	9.544%	$169.5741	$169.57	$169.55	$169.60
Purchase #2	$65.86	9.871%	$72.361	$72.36	$72.35	$72.40
Purchase #3	$58.38	10.261%	$64.3704	$64.37	$64.35	$64.40
Purchase #4	$222.31	8.444%	$241.0819	$241.08	$241.10	$241.10
Purchase #5	$22.55	12.686%	$25.4107	$25.41	$25.40	$25.40
Purchase #6	$145.92	6.445%	$155.3245	$155.32	$155.30	$155.30
Purchase #7	$88.70	13.264%	$100.4652	$100.47	$100.45	$100.50
7 purchase totals =	$758.52		$828.5878	$828.58	$828.50	$828.70