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	$228.40	6.672%	$243.6388	$243.64	$243.65	$243.60
Purchase #2	$37.41	5.381%	$39.423	$39.42	$39.40	$39.40
Purchase #3	$116.47	13.610%	$132.3216	$132.32	$132.30	$132.30
Purchase #4	$180.29	5.352%	$189.9391	$189.94	$189.95	$189.90
Purchase #5	$164.50	4.464%	$171.8433	$171.84	$171.85	$171.80
Purchase #6	$130.25	7.674%	$140.2454	$140.25	$140.25	$140.20
Purchase #7	$115.79	6.802%	$123.666	$123.67	$123.65	$123.70
7 purchase totals =	$973.11		$1,041.0772	$1,041.08	$1,041.05	$1,040.90