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	$96.69	7.785%	$104.2173	$104.22	$104.20	$104.20
Purchase #2	$201.51	9.830%	$221.3184	$221.32	$221.30	$221.30
Purchase #3	$77.25	13.820%	$87.926	$87.93	$87.95	$87.90
Purchase #4	$187.71	9.387%	$205.3303	$205.33	$205.35	$205.30
Purchase #5	$85.64	4.577%	$89.5597	$89.56	$89.55	$89.60
Purchase #6	$195.28	7.200%	$209.3402	$209.34	$209.35	$209.30
Purchase #7	$223.52	4.667%	$233.9517	$233.95	$233.95	$234.00
7 purchase totals =	$1,067.60		$1,151.6436	$1,151.65	$1,151.65	$1,151.60