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	$113.54	3.222%	$117.1983	$117.20	$117.20	$117.20
Purchase #2	$152.69	6.142%	$162.0682	$162.07	$162.05	$162.10
Purchase #3	$17.47	6.571%	$18.618	$18.62	$18.60	$18.60
Purchase #4	$107.28	11.768%	$119.9047	$119.90	$119.90	$119.90
Purchase #5	$224.32	11.401%	$249.8947	$249.89	$249.90	$249.90
Purchase #6	$38.67	11.486%	$43.1116	$43.11	$43.10	$43.10
Purchase #7	$154.79	7.165%	$165.8807	$165.88	$165.90	$165.90
7 purchase totals =	$808.76		$876.6762	$876.67	$876.65	$876.70