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	$86.30	3.207%	$89.0676	$89.07	$89.05	$89.10
Purchase #2	$136.35	9.178%	$148.8642	$148.86	$148.85	$148.90
Purchase #3	$140.94	4.440%	$147.1977	$147.20	$147.20	$147.20
Purchase #4	$31.67	5.127%	$33.2937	$33.29	$33.30	$33.30
Purchase #5	$57.35	13.810%	$65.27	$65.27	$65.25	$65.30
Purchase #6	$55.49	10.358%	$61.2377	$61.24	$61.25	$61.20
Purchase #7	$194.72	9.438%	$213.0977	$213.10	$213.10	$213.10
7 purchase totals =	$702.82		$758.0286	$758.03	$758.00	$758.10