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	$79.78	8.457%	$86.527	$86.53	$86.55	$86.50
Purchase #2	$225.54	10.500%	$249.2217	$249.22	$249.20	$249.20
Purchase #3	$145.97	8.699%	$158.6679	$158.67	$158.65	$158.70
Purchase #4	$55.63	6.151%	$59.0518	$59.05	$59.05	$59.10
Purchase #5	$240.41	13.331%	$272.4591	$272.46	$272.45	$272.50
Purchase #6	$170.45	12.630%	$191.9778	$191.98	$192.00	$192.00
Purchase #7	$38.67	10.715%	$42.8135	$42.81	$42.80	$42.80
7 purchase totals =	$956.45		$1,060.7188	$1,060.72	$1,060.70	$1,060.80