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	$216.86	5.135%	$227.9958	$228.00	$228.00	$228.00
Purchase #2	$103.42	7.529%	$111.2065	$111.21	$111.20	$111.20
Purchase #3	$234.46	6.815%	$250.4384	$250.44	$250.45	$250.40
Purchase #4	$63.91	5.733%	$67.574	$67.57	$67.55	$67.60
Purchase #5	$55.53	13.176%	$62.8466	$62.85	$62.85	$62.80
Purchase #6	$10.27	12.439%	$11.5475	$11.55	$11.55	$11.50
Purchase #7	$105.70	5.404%	$111.412	$111.41	$111.40	$111.40
7 purchase totals =	$790.15		$843.0208	$843.03	$843.00	$842.90