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	$131.33	11.356%	$146.2438	$146.24	$146.25	$146.20
Purchase #2	$139.90	13.118%	$158.2521	$158.25	$158.25	$158.30
Purchase #3	$96.36	7.478%	$103.5658	$103.57	$103.55	$103.60
Purchase #4	$149.83	13.860%	$170.5964	$170.60	$170.60	$170.60
Purchase #5	$134.35	13.788%	$152.8742	$152.87	$152.85	$152.90
Purchase #6	$95.27	10.873%	$105.6287	$105.63	$105.65	$105.60
Purchase #7	$131.53	11.569%	$146.7467	$146.75	$146.75	$146.70
7 purchase totals =	$878.57		$983.9077	$983.91	$983.90	$983.90