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	$81.82	12.563%	$92.099	$92.10	$92.10	$92.10
Purchase #2	$64.31	3.796%	$66.7512	$66.75	$66.75	$66.80
Purchase #3	$228.80	10.780%	$253.4646	$253.46	$253.45	$253.50
Purchase #4	$64.40	12.764%	$72.62	$72.62	$72.60	$72.60
Purchase #5	$209.34	5.799%	$221.4796	$221.48	$221.50	$221.50
Purchase #6	$6.26	13.292%	$7.0921	$7.09	$7.10	$7.10
Purchase #7	$144.66	11.183%	$160.8373	$160.84	$160.85	$160.80
7 purchase totals =	$799.59		$874.3438	$874.34	$874.35	$874.40