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	$114.53	11.628%	$127.8475	$127.85	$127.85	$127.80
Purchase #2	$109.76	4.385%	$114.573	$114.57	$114.55	$114.60
Purchase #3	$130.44	7.229%	$139.8695	$139.87	$139.85	$139.90
Purchase #4	$67.57	11.595%	$75.4047	$75.40	$75.40	$75.40
Purchase #5	$157.65	7.670%	$169.7418	$169.74	$169.75	$169.70
Purchase #6	$115.88	3.870%	$120.3646	$120.36	$120.35	$120.40
Purchase #7	$116.78	5.412%	$123.1001	$123.10	$123.10	$123.10
7 purchase totals =	$812.61		$870.9012	$870.89	$870.85	$870.90