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	$199.76	12.694%	$225.1175	$225.12	$225.10	$225.10
Purchase #2	$141.58	7.739%	$152.5369	$152.54	$152.55	$152.50
Purchase #3	$56.57	7.621%	$60.8812	$60.88	$60.90	$60.90
Purchase #4	$59.31	11.857%	$66.3424	$66.34	$66.35	$66.30
Purchase #5	$241.76	12.480%	$271.9316	$271.93	$271.95	$271.90
Purchase #6	$59.30	11.767%	$66.2778	$66.28	$66.30	$66.30
Purchase #7	$162.51	8.278%	$175.9626	$175.96	$175.95	$176.00
7 purchase totals =	$920.79		$1,019.0500	$1,019.05	$1,019.10	$1,019.00