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	$82.97	3.237%	$85.6557	$85.66	$85.65	$85.70
Purchase #2	$98.47	3.777%	$102.1892	$102.19	$102.20	$102.20
Purchase #3	$139.79	10.640%	$154.6637	$154.66	$154.65	$154.70
Purchase #4	$133.39	12.852%	$150.5333	$150.53	$150.55	$150.50
Purchase #5	$215.33	11.694%	$240.5107	$240.51	$240.50	$240.50
Purchase #6	$130.27	5.417%	$137.3267	$137.33	$137.35	$137.30
Purchase #7	$134.48	3.784%	$139.5687	$139.57	$139.55	$139.60
7 purchase totals =	$934.70		$1,010.4480	$1,010.45	$1,010.45	$1,010.50