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	$242.66	8.732%	$263.8491	$263.85	$263.85	$263.80
Purchase #2	$239.47	13.400%	$271.559	$271.56	$271.55	$271.60
Purchase #3	$218.71	13.697%	$248.6667	$248.67	$248.65	$248.70
Purchase #4	$60.63	11.374%	$67.5261	$67.53	$67.55	$67.50
Purchase #5	$41.38	5.381%	$43.6067	$43.61	$43.60	$43.60
Purchase #6	$148.54	3.861%	$154.2751	$154.28	$154.30	$154.30
Purchase #7	$152.77	10.507%	$168.8215	$168.82	$168.80	$168.80
7 purchase totals =	$1,104.16		$1,218.3042	$1,218.32	$1,218.30	$1,218.30