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	$117.33	8.178%	$126.9252	$126.93	$126.95	$126.90
Purchase #2	$84.81	6.850%	$90.6195	$90.62	$90.60	$90.60
Purchase #3	$65.95	9.630%	$72.301	$72.30	$72.30	$72.30
Purchase #4	$88.99	11.386%	$99.1224	$99.12	$99.10	$99.10
Purchase #5	$64.55	9.811%	$70.883	$70.88	$70.90	$70.90
Purchase #6	$16.51	6.609%	$17.6011	$17.60	$17.60	$17.60
Purchase #7	$54.26	6.224%	$57.6371	$57.64	$57.65	$57.60
7 purchase totals =	$492.40		$535.0893	$535.09	$535.10	$535.00