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	$85.56	13.287%	$96.9284	$96.93	$96.95	$96.90
Purchase #2	$41.73	13.302%	$47.2809	$47.28	$47.30	$47.30
Purchase #3	$136.69	13.873%	$155.653	$155.65	$155.65	$155.70
Purchase #4	$81.98	10.822%	$90.8519	$90.85	$90.85	$90.90
Purchase #5	$213.41	13.655%	$242.5511	$242.55	$242.55	$242.60
Purchase #6	$154.99	11.354%	$172.5876	$172.59	$172.60	$172.60
Purchase #7	$37.26	5.833%	$39.4334	$39.43	$39.45	$39.40
7 purchase totals =	$751.62		$845.2863	$845.28	$845.35	$845.40