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	$164.89	6.454%	$175.532	$175.53	$175.55	$175.50
Purchase #2	$18.70	8.587%	$20.3058	$20.31	$20.30	$20.30
Purchase #3	$230.32	4.345%	$240.3274	$240.33	$240.35	$240.30
Purchase #4	$199.71	10.387%	$220.4539	$220.45	$220.45	$220.50
Purchase #5	$169.95	12.461%	$191.1275	$191.13	$191.15	$191.10
Purchase #6	$123.48	8.742%	$134.2746	$134.27	$134.25	$134.30
Purchase #7	$93.41	7.333%	$100.2598	$100.26	$100.25	$100.30
7 purchase totals =	$1,000.46		$1,082.2810	$1,082.28	$1,082.30	$1,082.30