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	$93.64	3.425%	$96.8472	$96.85	$96.85	$96.80
Purchase #2	$137.49	7.801%	$148.2156	$148.22	$148.20	$148.20
Purchase #3	$62.50	5.116%	$65.6975	$65.70	$65.70	$65.70
Purchase #4	$206.33	7.747%	$222.3144	$222.31	$222.30	$222.30
Purchase #5	$147.79	3.677%	$153.2242	$153.22	$153.20	$153.20
Purchase #6	$38.27	6.561%	$40.7809	$40.78	$40.80	$40.80
Purchase #7	$173.39	5.420%	$182.7877	$182.79	$182.80	$182.80
7 purchase totals =	$859.41		$909.8675	$909.87	$909.85	$909.80