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	$182.68	13.109%	$206.6275	$206.63	$206.65	$206.60
Purchase #2	$245.60	6.851%	$262.4261	$262.43	$262.45	$262.40
Purchase #3	$15.39	5.646%	$16.2589	$16.26	$16.25	$16.30
Purchase #4	$137.32	7.320%	$147.3718	$147.37	$147.35	$147.40
Purchase #5	$96.76	6.776%	$103.3165	$103.32	$103.30	$103.30
Purchase #6	$90.86	5.531%	$95.8855	$95.89	$95.90	$95.90
Purchase #7	$61.82	5.510%	$65.2263	$65.23	$65.25	$65.20
7 purchase totals =	$830.43		$897.1126	$897.13	$897.15	$897.10