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	$63.66	13.242%	$72.0899	$72.09	$72.10	$72.10
Purchase #2	$234.98	8.238%	$254.3377	$254.34	$254.35	$254.30
Purchase #3	$57.77	6.502%	$61.5262	$61.53	$61.55	$61.50
Purchase #4	$91.70	4.478%	$95.8063	$95.81	$95.80	$95.80
Purchase #5	$191.91	9.788%	$210.6942	$210.69	$210.70	$210.70
Purchase #6	$139.90	6.127%	$148.4717	$148.47	$148.45	$148.50
Purchase #7	$226.97	10.180%	$250.0755	$250.08	$250.10	$250.10
7 purchase totals =	$1,006.89		$1,093.0015	$1,093.01	$1,093.05	$1,093.00