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	$184.77	12.682%	$208.2025	$208.20	$208.20	$208.20
Purchase #2	$113.73	10.662%	$125.8559	$125.86	$125.85	$125.90
Purchase #3	$65.62	9.571%	$71.9005	$71.90	$71.90	$71.90
Purchase #4	$249.89	6.135%	$265.2208	$265.22	$265.20	$265.20
Purchase #5	$98.85	4.342%	$103.1421	$103.14	$103.15	$103.10
Purchase #6	$85.39	11.773%	$95.443	$95.44	$95.45	$95.40
Purchase #7	$136.33	12.137%	$152.8764	$152.88	$152.90	$152.90
7 purchase totals =	$934.58		$1,022.6412	$1,022.64	$1,022.65	$1,022.60