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	$86.28	11.110%	$95.8657	$95.87	$95.85	$95.90
Purchase #2	$142.41	8.607%	$154.6672	$154.67	$154.65	$154.70
Purchase #3	$121.85	7.805%	$131.3604	$131.36	$131.35	$131.40
Purchase #4	$52.95	11.503%	$59.0408	$59.04	$59.05	$59.00
Purchase #5	$149.34	13.425%	$169.3889	$169.39	$169.40	$169.40
Purchase #6	$49.42	8.788%	$53.763	$53.76	$53.75	$53.80
Purchase #7	$103.94	8.164%	$112.4257	$112.43	$112.45	$112.40
7 purchase totals =	$706.19		$776.5117	$776.52	$776.50	$776.60