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	$144.40	4.376%	$150.7189	$150.72	$150.70	$150.70
Purchase #2	$108.78	4.515%	$113.6914	$113.69	$113.70	$113.70
Purchase #3	$96.82	13.106%	$109.5092	$109.51	$109.50	$109.50
Purchase #4	$109.86	13.263%	$124.4307	$124.43	$124.45	$124.40
Purchase #5	$87.35	10.771%	$96.7585	$96.76	$96.75	$96.80
Purchase #6	$126.44	13.759%	$143.8369	$143.84	$143.85	$143.80
Purchase #7	$172.72	5.563%	$182.3284	$182.33	$182.35	$182.30
7 purchase totals =	$846.37		$921.2740	$921.28	$921.30	$921.20