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	$103.51	5.243%	$108.937	$108.94	$108.95	$108.90
Purchase #2	$127.86	10.190%	$140.8889	$140.89	$140.90	$140.90
Purchase #3	$84.48	6.591%	$90.0481	$90.05	$90.05	$90.00
Purchase #4	$119.76	6.636%	$127.7073	$127.71	$127.70	$127.70
Purchase #5	$190.30	9.684%	$208.7287	$208.73	$208.75	$208.70
Purchase #6	$249.32	7.203%	$267.2785	$267.28	$267.30	$267.30
Purchase #7	$144.34	4.279%	$150.5163	$150.52	$150.50	$150.50
7 purchase totals =	$1,019.57		$1,094.1048	$1,094.12	$1,094.15	$1,094.00