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	$75.84	12.830%	$85.5703	$85.57	$85.55	$85.60
Purchase #2	$193.59	7.802%	$208.6939	$208.69	$208.70	$208.70
Purchase #3	$138.49	6.383%	$147.3298	$147.33	$147.35	$147.30
Purchase #4	$123.55	11.265%	$137.4679	$137.47	$137.45	$137.50
Purchase #5	$148.61	11.403%	$165.556	$165.56	$165.55	$165.60
Purchase #6	$129.80	12.417%	$145.9173	$145.92	$145.90	$145.90
Purchase #7	$122.39	4.481%	$127.8743	$127.87	$127.85	$127.90
7 purchase totals =	$932.27		$1,018.4095	$1,018.41	$1,018.35	$1,018.50