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	$179.27	11.638%	$200.1334	$200.13	$200.15	$200.10
Purchase #2	$109.72	4.572%	$114.7364	$114.74	$114.75	$114.70
Purchase #3	$34.77	7.468%	$37.3666	$37.37	$37.35	$37.40
Purchase #4	$233.89	10.252%	$257.8684	$257.87	$257.85	$257.90
Purchase #5	$161.30	13.625%	$183.2771	$183.28	$183.30	$183.30
Purchase #6	$88.66	13.808%	$100.9022	$100.90	$100.90	$100.90
Purchase #7	$33.87	13.478%	$38.435	$38.44	$38.45	$38.40
7 purchase totals =	$841.48		$932.7191	$932.73	$932.75	$932.70