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	$100.75	13.200%	$114.049	$114.05	$114.05	$114.00
Purchase #2	$93.56	12.196%	$104.9706	$104.97	$104.95	$105.00
Purchase #3	$235.85	3.151%	$243.2816	$243.28	$243.30	$243.30
Purchase #4	$78.71	8.618%	$85.4932	$85.49	$85.50	$85.50
Purchase #5	$144.86	4.417%	$151.2585	$151.26	$151.25	$151.30
Purchase #6	$155.83	12.554%	$175.3929	$175.39	$175.40	$175.40
Purchase #7	$38.81	4.461%	$40.5413	$40.54	$40.55	$40.50
7 purchase totals =	$848.37		$914.9871	$914.98	$915.00	$915.00