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	$49.90	6.471%	$53.129	$53.13	$53.15	$53.10
Purchase #2	$90.35	10.109%	$99.4835	$99.48	$99.50	$99.50
Purchase #3	$249.96	10.677%	$276.6482	$276.65	$276.65	$276.60
Purchase #4	$47.79	11.817%	$53.4373	$53.44	$53.45	$53.40
Purchase #5	$248.77	3.173%	$256.6635	$256.66	$256.65	$256.70
Purchase #6	$89.57	3.844%	$93.0131	$93.01	$93.00	$93.00
Purchase #7	$245.35	7.141%	$262.8704	$262.87	$262.85	$262.90
7 purchase totals =	$1,021.69		$1,095.2450	$1,095.24	$1,095.25	$1,095.20