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	$200.87	6.163%	$213.2496	$213.25	$213.25	$213.20
Purchase #2	$133.54	13.712%	$151.851	$151.85	$151.85	$151.90
Purchase #3	$30.83	8.127%	$33.3356	$33.34	$33.35	$33.30
Purchase #4	$136.25	11.728%	$152.2294	$152.23	$152.25	$152.20
Purchase #5	$170.72	11.585%	$190.4979	$190.50	$190.50	$190.50
Purchase #6	$130.46	4.497%	$136.3268	$136.33	$136.35	$136.30
Purchase #7	$229.77	7.714%	$247.4945	$247.49	$247.50	$247.50
7 purchase totals =	$1,032.44		$1,124.9848	$1,124.99	$1,125.05	$1,124.90