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	$59.70	3.495%	$61.7865	$61.79	$61.80	$61.80
Purchase #2	$174.45	7.484%	$187.5058	$187.51	$187.50	$187.50
Purchase #3	$164.69	4.289%	$171.7536	$171.75	$171.75	$171.80
Purchase #4	$56.29	13.455%	$63.8638	$63.86	$63.85	$63.90
Purchase #5	$191.29	10.222%	$210.8437	$210.84	$210.85	$210.80
Purchase #6	$176.48	7.415%	$189.566	$189.57	$189.55	$189.60
Purchase #7	$45.53	11.817%	$50.9103	$50.91	$50.90	$50.90
7 purchase totals =	$868.43		$936.2297	$936.23	$936.20	$936.30