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	$243.44	8.824%	$264.9211	$264.92	$264.90	$264.90
Purchase #2	$101.89	13.642%	$115.7898	$115.79	$115.80	$115.80
Purchase #3	$141.86	7.498%	$152.4967	$152.50	$152.50	$152.50
Purchase #4	$153.37	7.629%	$165.0706	$165.07	$165.05	$165.10
Purchase #5	$102.57	13.764%	$116.6877	$116.69	$116.70	$116.70
Purchase #6	$103.61	4.610%	$108.3864	$108.39	$108.40	$108.40
Purchase #7	$128.58	9.307%	$140.5469	$140.55	$140.55	$140.50
7 purchase totals =	$975.32		$1,063.8992	$1,063.91	$1,063.90	$1,063.90