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	$145.62	3.116%	$150.1575	$150.16	$150.15	$150.20
Purchase #2	$186.27	13.722%	$211.83	$211.83	$211.85	$211.80
Purchase #3	$79.98	9.652%	$87.6997	$87.70	$87.70	$87.70
Purchase #4	$95.84	4.869%	$100.5064	$100.51	$100.50	$100.50
Purchase #5	$188.29	11.115%	$209.2184	$209.22	$209.20	$209.20
Purchase #6	$80.93	10.476%	$89.4082	$89.41	$89.40	$89.40
Purchase #7	$164.61	6.721%	$175.6734	$175.67	$175.65	$175.70
7 purchase totals =	$941.54		$1,024.4936	$1,024.50	$1,024.45	$1,024.50