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	$231.27	8.427%	$250.7591	$250.76	$250.75	$250.80
Purchase #2	$206.81	7.847%	$223.0384	$223.04	$223.05	$223.00
Purchase #3	$210.54	13.583%	$239.1376	$239.14	$239.15	$239.10
Purchase #4	$127.37	12.658%	$143.4925	$143.49	$143.50	$143.50
Purchase #5	$28.86	7.624%	$31.0603	$31.06	$31.05	$31.10
Purchase #6	$7.69	10.213%	$8.4754	$8.48	$8.50	$8.50
Purchase #7	$148.45	11.232%	$165.1239	$165.12	$165.10	$165.10
7 purchase totals =	$960.99		$1,061.0872	$1,061.09	$1,061.10	$1,061.10