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	$125.59	4.722%	$131.5204	$131.52	$131.50	$131.50
Purchase #2	$176.92	8.428%	$191.8308	$191.83	$191.85	$191.80
Purchase #3	$57.46	3.648%	$59.5561	$59.56	$59.55	$59.60
Purchase #4	$65.88	9.713%	$72.2789	$72.28	$72.30	$72.30
Purchase #5	$178.33	4.691%	$186.6955	$186.70	$186.70	$186.70
Purchase #6	$49.47	11.326%	$55.073	$55.07	$55.05	$55.10
Purchase #7	$39.30	10.218%	$43.3157	$43.32	$43.30	$43.30
7 purchase totals =	$692.95		$740.2704	$740.28	$740.25	$740.30