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	$99.29	7.315%	$106.5531	$106.55	$106.55	$106.60
Purchase #2	$39.68	13.796%	$45.1543	$45.15	$45.15	$45.20
Purchase #3	$156.96	3.784%	$162.8994	$162.90	$162.90	$162.90
Purchase #4	$162.74	8.678%	$176.8626	$176.86	$176.85	$176.90
Purchase #5	$234.78	12.709%	$264.6182	$264.62	$264.60	$264.60
Purchase #6	$137.33	9.854%	$150.8625	$150.86	$150.85	$150.90
Purchase #7	$125.26	11.503%	$139.6687	$139.67	$139.65	$139.70
7 purchase totals =	$956.04		$1,046.6188	$1,046.61	$1,046.55	$1,046.80