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	$54.52	12.412%	$61.287	$61.29	$61.30	$61.30
Purchase #2	$174.77	9.416%	$191.2263	$191.23	$191.25	$191.20
Purchase #3	$69.89	5.637%	$73.8297	$73.83	$73.85	$73.80
Purchase #4	$98.30	3.181%	$101.4269	$101.43	$101.45	$101.40
Purchase #5	$57.67	3.222%	$59.5281	$59.53	$59.55	$59.50
Purchase #6	$59.87	3.429%	$61.9229	$61.92	$61.90	$61.90
Purchase #7	$184.93	3.700%	$191.7724	$191.77	$191.75	$191.80
7 purchase totals =	$699.95		$740.9933	$741.00	$741.05	$740.90