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	$76.80	3.313%	$79.3444	$79.34	$79.35	$79.30
Purchase #2	$10.96	13.687%	$12.4601	$12.46	$12.45	$12.50
Purchase #3	$208.63	4.378%	$217.7638	$217.76	$217.75	$217.80
Purchase #4	$39.31	8.165%	$42.5197	$42.52	$42.50	$42.50
Purchase #5	$76.42	12.771%	$86.1796	$86.18	$86.20	$86.20
Purchase #6	$171.75	11.541%	$191.5717	$191.57	$191.55	$191.60
Purchase #7	$72.95	13.440%	$82.7545	$82.75	$82.75	$82.80
7 purchase totals =	$656.82		$712.5938	$712.58	$712.55	$712.70