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	$232.88	6.275%	$247.4932	$247.49	$247.50	$247.50
Purchase #2	$5.26	6.601%	$5.6072	$5.61	$5.60	$5.60
Purchase #3	$37.71	13.362%	$42.7488	$42.75	$42.75	$42.70
Purchase #4	$82.47	3.493%	$85.3507	$85.35	$85.35	$85.40
Purchase #5	$32.72	8.660%	$35.5536	$35.55	$35.55	$35.60
Purchase #6	$56.25	10.403%	$62.1017	$62.10	$62.10	$62.10
Purchase #7	$126.30	10.742%	$139.8671	$139.87	$139.85	$139.90
7 purchase totals =	$573.59		$618.7223	$618.72	$618.70	$618.80