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	$80.29	7.131%	$86.0155	$86.02	$86.00	$86.00
Purchase #2	$199.37	12.289%	$223.8706	$223.87	$223.85	$223.90
Purchase #3	$171.50	9.203%	$187.2831	$187.28	$187.30	$187.30
Purchase #4	$165.42	5.842%	$175.0838	$175.08	$175.10	$175.10
Purchase #5	$168.44	13.313%	$190.8644	$190.86	$190.85	$190.90
Purchase #6	$217.90	9.286%	$238.1342	$238.13	$238.15	$238.10
Purchase #7	$215.31	11.546%	$240.1697	$240.17	$240.15	$240.20
7 purchase totals =	$1,218.23		$1,341.4213	$1,341.41	$1,341.40	$1,341.50