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	$121.63	7.640%	$130.9225	$130.92	$130.90	$130.90
Purchase #2	$58.26	9.747%	$63.9386	$63.94	$63.95	$63.90
Purchase #3	$236.53	13.244%	$267.856	$267.86	$267.85	$267.90
Purchase #4	$103.30	12.639%	$116.3561	$116.36	$116.35	$116.40
Purchase #5	$38.72	10.613%	$42.8294	$42.83	$42.85	$42.80
Purchase #6	$69.88	3.502%	$72.3272	$72.33	$72.35	$72.30
Purchase #7	$185.43	11.586%	$206.9139	$206.91	$206.90	$206.90
7 purchase totals =	$813.75		$901.1437	$901.15	$901.15	$901.10