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	$61.31	3.486%	$63.4473	$63.45	$63.45	$63.40
Purchase #2	$158.71	7.638%	$170.8323	$170.83	$170.85	$170.80
Purchase #3	$89.73	11.281%	$99.8524	$99.85	$99.85	$99.90
Purchase #4	$176.45	8.536%	$191.5118	$191.51	$191.50	$191.50
Purchase #5	$227.84	4.178%	$237.3592	$237.36	$237.35	$237.40
Purchase #6	$107.53	13.790%	$122.3584	$122.36	$122.35	$122.40
Purchase #7	$125.30	4.674%	$131.1565	$131.16	$131.15	$131.20
7 purchase totals =	$946.87		$1,016.5179	$1,016.52	$1,016.50	$1,016.60