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	$143.29	3.828%	$148.7751	$148.78	$148.80	$148.80
Purchase #2	$127.97	6.708%	$136.5542	$136.55	$136.55	$136.60
Purchase #3	$104.78	13.437%	$118.8593	$118.86	$118.85	$118.90
Purchase #4	$245.35	13.609%	$278.7397	$278.74	$278.75	$278.70
Purchase #5	$68.65	11.157%	$76.3093	$76.31	$76.30	$76.30
Purchase #6	$128.41	11.260%	$142.869	$142.87	$142.85	$142.90
Purchase #7	$226.42	12.834%	$255.4787	$255.48	$255.50	$255.50
7 purchase totals =	$1,044.87		$1,157.5853	$1,157.59	$1,157.60	$1,157.70