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	$83.85	10.741%	$92.8563	$92.86	$92.85	$92.90
Purchase #2	$139.96	11.779%	$156.4459	$156.45	$156.45	$156.40
Purchase #3	$181.26	12.635%	$204.1622	$204.16	$204.15	$204.20
Purchase #4	$139.41	12.541%	$156.8934	$156.89	$156.90	$156.90
Purchase #5	$213.75	3.505%	$221.2419	$221.24	$221.25	$221.20
Purchase #6	$160.39	7.237%	$171.9974	$172.00	$172.00	$172.00
Purchase #7	$52.61	13.550%	$59.7387	$59.74	$59.75	$59.70
7 purchase totals =	$971.23		$1,063.3358	$1,063.34	$1,063.35	$1,063.30