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	$191.67	8.725%	$208.3932	$208.39	$208.40	$208.40
Purchase #2	$111.57	11.625%	$124.54	$124.54	$124.55	$124.50
Purchase #3	$47.40	8.515%	$51.4361	$51.44	$51.45	$51.40
Purchase #4	$64.82	4.197%	$67.5405	$67.54	$67.55	$67.50
Purchase #5	$92.29	11.786%	$103.1673	$103.17	$103.15	$103.20
Purchase #6	$159.70	8.179%	$172.7619	$172.76	$172.75	$172.80
Purchase #7	$176.88	11.514%	$197.246	$197.25	$197.25	$197.20
7 purchase totals =	$844.33		$925.0850	$925.09	$925.10	$925.00