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	$131.46	4.160%	$136.9287	$136.93	$136.95	$136.90
Purchase #2	$119.89	7.237%	$128.5664	$128.57	$128.55	$128.60
Purchase #3	$40.55	7.822%	$43.7218	$43.72	$43.70	$43.70
Purchase #4	$199.25	12.362%	$223.8813	$223.88	$223.90	$223.90
Purchase #5	$41.95	8.531%	$45.5288	$45.53	$45.55	$45.50
Purchase #6	$107.67	4.337%	$112.3396	$112.34	$112.35	$112.30
Purchase #7	$9.58	9.745%	$10.5136	$10.51	$10.50	$10.50
7 purchase totals =	$650.35		$701.4802	$701.48	$701.50	$701.40