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	$103.45	11.791%	$115.6478	$115.65	$115.65	$115.60
Purchase #2	$26.54	6.472%	$28.2577	$28.26	$28.25	$28.30
Purchase #3	$134.61	13.395%	$152.641	$152.64	$152.65	$152.60
Purchase #4	$158.94	8.526%	$172.4912	$172.49	$172.50	$172.50
Purchase #5	$190.34	13.614%	$216.2529	$216.25	$216.25	$216.30
Purchase #6	$247.44	9.520%	$270.9963	$271.00	$271.00	$271.00
Purchase #7	$168.77	10.142%	$185.8867	$185.89	$185.90	$185.90
7 purchase totals =	$1,030.09		$1,142.1736	$1,142.18	$1,142.20	$1,142.20