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	$90.58	4.585%	$94.7331	$94.73	$94.75	$94.70
Purchase #2	$52.75	12.277%	$59.2261	$59.23	$59.25	$59.20
Purchase #3	$116.42	13.242%	$131.8363	$131.84	$131.85	$131.80
Purchase #4	$71.42	9.230%	$78.0121	$78.01	$78.00	$78.00
Purchase #5	$90.44	5.568%	$95.4757	$95.48	$95.50	$95.50
Purchase #6	$209.52	7.521%	$225.278	$225.28	$225.30	$225.30
Purchase #7	$45.64	7.384%	$49.0101	$49.01	$49.00	$49.00
7 purchase totals =	$676.77		$733.5714	$733.58	$733.65	$733.50