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	$114.92	7.334%	$123.3482	$123.35	$123.35	$123.30
Purchase #2	$40.32	10.637%	$44.6088	$44.61	$44.60	$44.60
Purchase #3	$37.83	11.364%	$42.129	$42.13	$42.15	$42.10
Purchase #4	$117.44	13.715%	$133.5469	$133.55	$133.55	$133.50
Purchase #5	$203.25	9.838%	$223.2457	$223.25	$223.25	$223.20
Purchase #6	$238.73	12.383%	$268.2919	$268.29	$268.30	$268.30
Purchase #7	$118.63	4.126%	$123.5247	$123.52	$123.50	$123.50
7 purchase totals =	$871.12		$958.6952	$958.70	$958.70	$958.50