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	$116.58	6.831%	$124.5436	$124.54	$124.55	$124.50
Purchase #2	$127.52	4.616%	$133.4063	$133.41	$133.40	$133.40
Purchase #3	$201.60	11.400%	$224.5824	$224.58	$224.60	$224.60
Purchase #4	$57.55	3.594%	$59.6183	$59.62	$59.60	$59.60
Purchase #5	$17.49	5.719%	$18.4903	$18.49	$18.50	$18.50
Purchase #6	$121.98	5.162%	$128.2766	$128.28	$128.30	$128.30
Purchase #7	$165.50	5.171%	$174.058	$174.06	$174.05	$174.10
7 purchase totals =	$808.22		$862.9755	$862.98	$863.00	$863.00