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	$53.98	10.225%	$59.4995	$59.50	$59.50	$59.50
Purchase #2	$86.82	12.443%	$97.623	$97.62	$97.60	$97.60
Purchase #3	$169.68	10.747%	$187.9155	$187.92	$187.90	$187.90
Purchase #4	$246.83	3.744%	$256.0713	$256.07	$256.05	$256.10
Purchase #5	$166.54	9.750%	$182.7777	$182.78	$182.80	$182.80
Purchase #6	$110.30	13.373%	$125.0504	$125.05	$125.05	$125.10
Purchase #7	$89.36	11.717%	$99.8303	$99.83	$99.85	$99.80
7 purchase totals =	$923.51		$1,008.7677	$1,008.77	$1,008.75	$1,008.80