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	$165.46	4.326%	$172.6178	$172.62	$172.60	$172.60
Purchase #2	$200.85	13.816%	$228.5994	$228.60	$228.60	$228.60
Purchase #3	$34.31	4.334%	$35.797	$35.80	$35.80	$35.80
Purchase #4	$190.87	5.162%	$200.7227	$200.72	$200.70	$200.70
Purchase #5	$135.69	11.354%	$151.0962	$151.10	$151.10	$151.10
Purchase #6	$94.46	10.782%	$104.6447	$104.64	$104.65	$104.60
Purchase #7	$34.43	11.556%	$38.4087	$38.41	$38.40	$38.40
7 purchase totals =	$856.07		$931.8865	$931.89	$931.85	$931.80