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	$113.29	12.189%	$127.0989	$127.10	$127.10	$127.10
Purchase #2	$123.25	12.362%	$138.4862	$138.49	$138.50	$138.50
Purchase #3	$23.37	4.700%	$24.4684	$24.47	$24.45	$24.50
Purchase #4	$195.60	8.641%	$212.5018	$212.50	$212.50	$212.50
Purchase #5	$89.27	10.570%	$98.7058	$98.71	$98.70	$98.70
Purchase #6	$160.60	11.552%	$179.1525	$179.15	$179.15	$179.20
Purchase #7	$243.49	8.771%	$264.8465	$264.85	$264.85	$264.80
7 purchase totals =	$948.87		$1,045.2601	$1,045.27	$1,045.25	$1,045.30