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	$52.61	3.474%	$54.4377	$54.44	$54.45	$54.40
Purchase #2	$92.87	10.630%	$102.7421	$102.74	$102.75	$102.70
Purchase #3	$241.52	13.455%	$274.0165	$274.02	$274.00	$274.00
Purchase #4	$250.28	7.830%	$269.8769	$269.88	$269.90	$269.90
Purchase #5	$196.52	13.662%	$223.3686	$223.37	$223.35	$223.40
Purchase #6	$52.36	9.276%	$57.2169	$57.22	$57.20	$57.20
Purchase #7	$74.48	9.807%	$81.7843	$81.78	$81.80	$81.80
7 purchase totals =	$960.64		$1,063.4430	$1,063.45	$1,063.45	$1,063.40