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	$101.93	9.485%	$111.5981	$111.60	$111.60	$111.60
Purchase #2	$35.72	4.518%	$37.3338	$37.33	$37.35	$37.30
Purchase #3	$112.92	12.344%	$126.8588	$126.86	$126.85	$126.90
Purchase #4	$18.77	6.398%	$19.9709	$19.97	$19.95	$20.00
Purchase #5	$117.67	11.207%	$130.8573	$130.86	$130.85	$130.90
Purchase #6	$145.77	13.661%	$165.6836	$165.68	$165.70	$165.70
Purchase #7	$236.25	12.493%	$265.7647	$265.76	$265.75	$265.80
7 purchase totals =	$769.03		$858.0672	$858.06	$858.05	$858.20