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	$59.75	8.125%	$64.6047	$64.60	$64.60	$64.60
Purchase #2	$114.85	10.777%	$127.2274	$127.23	$127.25	$127.20
Purchase #3	$139.97	8.129%	$151.3482	$151.35	$151.35	$151.30
Purchase #4	$115.33	13.378%	$130.7588	$130.76	$130.75	$130.80
Purchase #5	$170.44	11.768%	$190.4974	$190.50	$190.50	$190.50
Purchase #6	$154.66	13.706%	$175.8577	$175.86	$175.85	$175.90
Purchase #7	$171.26	11.292%	$190.5987	$190.60	$190.60	$190.60
7 purchase totals =	$926.26		$1,030.8929	$1,030.90	$1,030.90	$1,030.90