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	$64.31	12.324%	$72.2356	$72.24	$72.25	$72.20
Purchase #2	$170.31	7.500%	$183.0833	$183.08	$183.10	$183.10
Purchase #3	$221.59	10.301%	$244.416	$244.42	$244.40	$244.40
Purchase #4	$69.57	13.460%	$78.9341	$78.93	$78.95	$78.90
Purchase #5	$225.75	8.490%	$244.9162	$244.92	$244.90	$244.90
Purchase #6	$170.26	12.821%	$192.089	$192.09	$192.10	$192.10
Purchase #7	$158.73	13.862%	$180.7332	$180.73	$180.75	$180.70
7 purchase totals =	$1,080.52		$1,196.4074	$1,196.41	$1,196.45	$1,196.30