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	$172.99	10.806%	$191.6833	$191.68	$191.70	$191.70
Purchase #2	$145.96	13.494%	$165.6558	$165.66	$165.65	$165.70
Purchase #3	$72.26	8.785%	$78.608	$78.61	$78.60	$78.60
Purchase #4	$196.79	6.389%	$209.3629	$209.36	$209.35	$209.40
Purchase #5	$114.58	8.154%	$123.9229	$123.92	$123.90	$123.90
Purchase #6	$167.69	9.189%	$183.099	$183.10	$183.10	$183.10
Purchase #7	$99.84	10.276%	$110.0996	$110.10	$110.10	$110.10
7 purchase totals =	$970.11		$1,062.4315	$1,062.43	$1,062.40	$1,062.50