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	$55.59	7.208%	$59.5969	$59.60	$59.60	$59.60
Purchase #2	$122.57	11.225%	$136.3285	$136.33	$136.35	$136.30
Purchase #3	$197.58	12.273%	$221.829	$221.83	$221.85	$221.80
Purchase #4	$24.89	12.769%	$28.0682	$28.07	$28.05	$28.10
Purchase #5	$140.76	10.457%	$155.4793	$155.48	$155.50	$155.50
Purchase #6	$163.97	6.219%	$174.1673	$174.17	$174.15	$174.20
Purchase #7	$223.69	8.371%	$242.4151	$242.42	$242.40	$242.40
7 purchase totals =	$929.05		$1,017.8843	$1,017.90	$1,017.90	$1,017.90