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	$46.80	4.376%	$48.848	$48.85	$48.85	$48.80
Purchase #2	$198.59	9.460%	$217.3766	$217.38	$217.40	$217.40
Purchase #3	$176.54	8.261%	$191.124	$191.12	$191.10	$191.10
Purchase #4	$174.83	5.792%	$184.9562	$184.96	$184.95	$185.00
Purchase #5	$173.60	6.336%	$184.5993	$184.60	$184.60	$184.60
Purchase #6	$72.28	5.803%	$76.4744	$76.47	$76.45	$76.50
Purchase #7	$94.76	9.871%	$104.1138	$104.11	$104.10	$104.10
7 purchase totals =	$937.40		$1,007.4923	$1,007.49	$1,007.45	$1,007.50