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	$187.42	6.553%	$199.7016	$199.70	$199.70	$199.70
Purchase #2	$90.32	4.263%	$94.1703	$94.17	$94.15	$94.20
Purchase #3	$36.40	12.357%	$40.8979	$40.90	$40.90	$40.90
Purchase #4	$41.70	13.364%	$47.2728	$47.27	$47.25	$47.30
Purchase #5	$207.75	4.382%	$216.8536	$216.85	$216.85	$216.90
Purchase #6	$76.73	11.135%	$85.2739	$85.27	$85.25	$85.30
Purchase #7	$107.55	4.485%	$112.3736	$112.37	$112.35	$112.40
7 purchase totals =	$747.87		$796.5437	$796.53	$796.45	$796.70