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	$79.43	8.385%	$86.0902	$86.09	$86.10	$86.10
Purchase #2	$12.96	3.443%	$13.4062	$13.41	$13.40	$13.40
Purchase #3	$94.69	9.449%	$103.6373	$103.64	$103.65	$103.60
Purchase #4	$168.45	4.641%	$176.2678	$176.27	$176.25	$176.30
Purchase #5	$17.41	3.789%	$18.0697	$18.07	$18.05	$18.10
Purchase #6	$17.89	4.110%	$18.6253	$18.63	$18.65	$18.60
Purchase #7	$80.98	9.232%	$88.4561	$88.46	$88.45	$88.50
7 purchase totals =	$471.81		$504.5526	$504.57	$504.55	$504.60