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	$34.92	6.288%	$37.1158	$37.12	$37.10	$37.10
Purchase #2	$22.84	11.572%	$25.483	$25.48	$25.50	$25.50
Purchase #3	$108.56	13.866%	$123.6129	$123.61	$123.60	$123.60
Purchase #4	$181.85	7.822%	$196.0743	$196.07	$196.05	$196.10
Purchase #5	$218.94	8.461%	$237.4645	$237.46	$237.45	$237.50
Purchase #6	$108.37	7.308%	$116.2897	$116.29	$116.30	$116.30
Purchase #7	$14.44	3.758%	$14.9827	$14.98	$15.00	$15.00
7 purchase totals =	$689.92		$751.0229	$751.01	$751.00	$751.10