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	$184.43	12.520%	$207.5206	$207.52	$207.50	$207.50
Purchase #2	$180.89	13.266%	$204.8869	$204.89	$204.90	$204.90
Purchase #3	$48.64	11.215%	$54.095	$54.10	$54.10	$54.10
Purchase #4	$91.66	6.653%	$97.7581	$97.76	$97.75	$97.80
Purchase #5	$218.83	3.170%	$225.7669	$225.77	$225.75	$225.80
Purchase #6	$73.38	13.162%	$83.0383	$83.04	$83.05	$83.00
Purchase #7	$110.80	11.636%	$123.6927	$123.69	$123.70	$123.70
7 purchase totals =	$908.63		$996.7585	$996.77	$996.75	$996.80