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	$133.78	10.683%	$148.0717	$148.07	$148.05	$148.10
Purchase #2	$124.59	13.799%	$141.7822	$141.78	$141.80	$141.80
Purchase #3	$38.43	3.224%	$39.669	$39.67	$39.65	$39.70
Purchase #4	$153.59	13.618%	$174.5059	$174.51	$174.50	$174.50
Purchase #5	$107.52	6.785%	$114.8152	$114.82	$114.80	$114.80
Purchase #6	$93.77	3.144%	$96.7181	$96.72	$96.70	$96.70
Purchase #7	$132.49	3.801%	$137.5259	$137.53	$137.55	$137.50
7 purchase totals =	$784.17		$853.0880	$853.10	$853.05	$853.10