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	$110.92	4.688%	$116.1199	$116.12	$116.10	$116.10
Purchase #2	$250.55	5.274%	$263.764	$263.76	$263.75	$263.80
Purchase #3	$132.85	13.597%	$150.9136	$150.91	$150.90	$150.90
Purchase #4	$19.50	4.761%	$20.4284	$20.43	$20.45	$20.40
Purchase #5	$47.95	9.365%	$52.4405	$52.44	$52.45	$52.40
Purchase #6	$90.63	11.388%	$100.9509	$100.95	$100.95	$101.00
Purchase #7	$205.42	12.356%	$230.8017	$230.80	$230.80	$230.80
7 purchase totals =	$857.82		$935.4190	$935.41	$935.40	$935.40