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	$134.67	12.768%	$151.8647	$151.86	$151.85	$151.90
Purchase #2	$93.56	11.712%	$104.5177	$104.52	$104.50	$104.50
Purchase #3	$95.99	9.175%	$104.7971	$104.80	$104.80	$104.80
Purchase #4	$86.30	3.570%	$89.3809	$89.38	$89.40	$89.40
Purchase #5	$225.64	3.589%	$233.7382	$233.74	$233.75	$233.70
Purchase #6	$133.95	7.197%	$143.5904	$143.59	$143.60	$143.60
Purchase #7	$244.30	3.635%	$253.1803	$253.18	$253.20	$253.20
7 purchase totals =	$1,014.41		$1,081.0693	$1,081.07	$1,081.10	$1,081.10