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	$82.54	12.652%	$92.983	$92.98	$93.00	$93.00
Purchase #2	$111.42	13.216%	$126.1453	$126.15	$126.15	$126.10
Purchase #3	$89.32	6.241%	$94.8945	$94.89	$94.90	$94.90
Purchase #4	$73.87	12.426%	$83.0491	$83.05	$83.05	$83.00
Purchase #5	$67.55	10.136%	$74.3969	$74.40	$74.40	$74.40
Purchase #6	$50.38	6.487%	$53.6482	$53.65	$53.65	$53.60
Purchase #7	$57.27	6.526%	$61.0074	$61.01	$61.00	$61.00
7 purchase totals =	$532.35		$586.1244	$586.13	$586.15	$586.00