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	$98.39	8.165%	$106.4235	$106.42	$106.40	$106.40
Purchase #2	$53.90	7.123%	$57.7393	$57.74	$57.75	$57.70
Purchase #3	$158.64	11.590%	$177.0264	$177.03	$177.05	$177.00
Purchase #4	$11.35	13.229%	$12.8515	$12.85	$12.85	$12.90
Purchase #5	$112.48	13.395%	$127.5467	$127.55	$127.55	$127.50
Purchase #6	$126.65	12.641%	$142.6598	$142.66	$142.65	$142.70
Purchase #7	$125.31	13.147%	$141.7845	$141.78	$141.80	$141.80
7 purchase totals =	$686.72		$766.0317	$766.03	$766.05	$766.00