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	$68.27	13.127%	$77.2318	$77.23	$77.25	$77.20
Purchase #2	$126.97	8.107%	$137.2635	$137.26	$137.25	$137.30
Purchase #3	$56.75	4.806%	$59.4774	$59.48	$59.50	$59.50
Purchase #4	$56.50	3.253%	$58.3379	$58.34	$58.35	$58.30
Purchase #5	$38.86	3.830%	$40.3483	$40.35	$40.35	$40.30
Purchase #6	$53.63	6.625%	$57.183	$57.18	$57.20	$57.20
Purchase #7	$28.94	13.790%	$32.9308	$32.93	$32.95	$32.90
7 purchase totals =	$429.92		$462.7727	$462.77	$462.85	$462.70