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	$233.92	11.478%	$260.7693	$260.77	$260.75	$260.80
Purchase #2	$88.44	8.342%	$95.8177	$95.82	$95.80	$95.80
Purchase #3	$61.39	6.833%	$65.5848	$65.58	$65.60	$65.60
Purchase #4	$167.79	3.281%	$173.2952	$173.30	$173.30	$173.30
Purchase #5	$74.74	4.813%	$78.3372	$78.34	$78.35	$78.30
Purchase #6	$110.56	13.658%	$125.6603	$125.66	$125.65	$125.70
Purchase #7	$100.31	5.217%	$105.5432	$105.54	$105.55	$105.50
7 purchase totals =	$837.15		$905.0077	$905.01	$905.00	$905.00