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	$99.50	6.601%	$106.068	$106.07	$106.05	$106.10
Purchase #2	$14.66	4.696%	$15.3484	$15.35	$15.35	$15.30
Purchase #3	$90.70	9.263%	$99.1015	$99.10	$99.10	$99.10
Purchase #4	$205.89	13.814%	$234.3316	$234.33	$234.35	$234.30
Purchase #5	$85.65	4.104%	$89.1651	$89.17	$89.15	$89.20
Purchase #6	$169.56	10.359%	$187.1247	$187.12	$187.10	$187.10
Purchase #7	$109.26	10.501%	$120.7334	$120.73	$120.75	$120.70
7 purchase totals =	$775.22		$851.8727	$851.87	$851.85	$851.80