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	$165.36	9.739%	$181.4644	$181.46	$181.45	$181.50
Purchase #2	$95.52	7.662%	$102.8387	$102.84	$102.85	$102.80
Purchase #3	$69.78	4.489%	$72.9124	$72.91	$72.90	$72.90
Purchase #4	$164.91	13.844%	$187.7401	$187.74	$187.75	$187.70
Purchase #5	$49.50	7.781%	$53.3516	$53.35	$53.35	$53.40
Purchase #6	$50.53	11.581%	$56.3819	$56.38	$56.40	$56.40
Purchase #7	$50.88	11.603%	$56.7836	$56.78	$56.80	$56.80
7 purchase totals =	$646.48		$711.4727	$711.46	$711.50	$711.50