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	$41.31	3.532%	$42.7691	$42.77	$42.75	$42.80
Purchase #2	$9.63	10.454%	$10.6367	$10.64	$10.65	$10.60
Purchase #3	$246.49	5.531%	$260.1234	$260.12	$260.10	$260.10
Purchase #4	$105.84	5.595%	$111.7617	$111.76	$111.75	$111.80
Purchase #5	$29.83	12.499%	$33.5585	$33.56	$33.55	$33.60
Purchase #6	$39.32	10.775%	$43.5567	$43.56	$43.55	$43.60
Purchase #7	$173.69	3.764%	$180.2277	$180.23	$180.25	$180.20
7 purchase totals =	$646.11		$682.6338	$682.64	$682.60	$682.70