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	$168.27	12.117%	$188.6593	$188.66	$188.65	$188.70
Purchase #2	$175.81	11.617%	$196.2338	$196.23	$196.25	$196.20
Purchase #3	$211.92	9.158%	$231.3276	$231.33	$231.35	$231.30
Purchase #4	$231.38	9.630%	$253.6619	$253.66	$253.65	$253.70
Purchase #5	$18.43	10.482%	$20.3618	$20.36	$20.35	$20.40
Purchase #6	$147.62	3.575%	$152.8974	$152.90	$152.90	$152.90
Purchase #7	$140.76	10.632%	$155.7256	$155.73	$155.75	$155.70
7 purchase totals =	$1,094.19		$1,198.8674	$1,198.87	$1,198.90	$1,198.90