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	$143.33	5.183%	$150.7588	$150.76	$150.75	$150.80
Purchase #2	$47.49	7.212%	$50.915	$50.92	$50.90	$50.90
Purchase #3	$98.45	13.210%	$111.4552	$111.46	$111.45	$111.50
Purchase #4	$122.86	10.771%	$136.0933	$136.09	$136.10	$136.10
Purchase #5	$41.81	4.836%	$43.8319	$43.83	$43.85	$43.80
Purchase #6	$67.92	13.134%	$76.8406	$76.84	$76.85	$76.80
Purchase #7	$52.30	4.223%	$54.5086	$54.51	$54.50	$54.50
7 purchase totals =	$574.16		$624.4034	$624.41	$624.40	$624.40