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	$93.77	11.668%	$104.7111	$104.71	$104.70	$104.70
Purchase #2	$65.92	13.539%	$74.8449	$74.84	$74.85	$74.80
Purchase #3	$227.87	11.295%	$253.6079	$253.61	$253.60	$253.60
Purchase #4	$168.94	11.609%	$188.5522	$188.55	$188.55	$188.60
Purchase #5	$183.65	9.333%	$200.7901	$200.79	$200.80	$200.80
Purchase #6	$39.51	6.334%	$42.0126	$42.01	$42.00	$42.00
Purchase #7	$221.47	3.456%	$229.124	$229.12	$229.10	$229.10
7 purchase totals =	$1,001.13		$1,093.6428	$1,093.63	$1,093.60	$1,093.60