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	$130.84	8.806%	$142.3618	$142.36	$142.35	$142.40
Purchase #2	$158.58	12.429%	$178.2899	$178.29	$178.30	$178.30
Purchase #3	$27.76	5.389%	$29.256	$29.26	$29.25	$29.30
Purchase #4	$220.46	3.370%	$227.8895	$227.89	$227.90	$227.90
Purchase #5	$156.71	5.370%	$165.1253	$165.13	$165.15	$165.10
Purchase #6	$156.64	9.346%	$171.2796	$171.28	$171.30	$171.30
Purchase #7	$123.81	12.464%	$139.2417	$139.24	$139.25	$139.20
7 purchase totals =	$974.80		$1,053.4438	$1,053.45	$1,053.50	$1,053.50