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	$59.26	13.706%	$67.3822	$67.38	$67.40	$67.40
Purchase #2	$250.96	5.185%	$263.9723	$263.97	$263.95	$264.00
Purchase #3	$39.49	5.252%	$41.564	$41.56	$41.55	$41.60
Purchase #4	$150.85	3.520%	$156.1599	$156.16	$156.15	$156.20
Purchase #5	$70.53	8.382%	$76.4418	$76.44	$76.45	$76.40
Purchase #6	$74.75	10.472%	$82.5778	$82.58	$82.60	$82.60
Purchase #7	$109.80	9.596%	$120.3364	$120.34	$120.35	$120.30
7 purchase totals =	$755.64		$808.4344	$808.43	$808.45	$808.50