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	$87.61	8.257%	$94.844	$94.84	$94.85	$94.80
Purchase #2	$124.83	3.421%	$129.1004	$129.10	$129.10	$129.10
Purchase #3	$165.64	10.231%	$182.5866	$182.59	$182.60	$182.60
Purchase #4	$169.65	12.262%	$190.4525	$190.45	$190.45	$190.50
Purchase #5	$19.55	6.146%	$20.7515	$20.75	$20.75	$20.80
Purchase #6	$124.36	7.414%	$133.5801	$133.58	$133.60	$133.60
Purchase #7	$239.62	10.531%	$264.8544	$264.85	$264.85	$264.90
7 purchase totals =	$931.26		$1,016.1695	$1,016.16	$1,016.20	$1,016.30