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	$141.31	6.813%	$150.9375	$150.94	$150.95	$150.90
Purchase #2	$93.44	9.746%	$102.5467	$102.55	$102.55	$102.50
Purchase #3	$143.86	6.666%	$153.4497	$153.45	$153.45	$153.40
Purchase #4	$96.29	13.467%	$109.2574	$109.26	$109.25	$109.30
Purchase #5	$40.27	4.598%	$42.1216	$42.12	$42.10	$42.10
Purchase #6	$64.78	8.407%	$70.2261	$70.23	$70.25	$70.20
Purchase #7	$61.44	7.414%	$65.9952	$66.00	$66.00	$66.00
7 purchase totals =	$641.39		$694.5342	$694.55	$694.55	$694.40