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	$41.39	12.577%	$46.5956	$46.60	$46.60	$46.60
Purchase #2	$119.58	12.705%	$134.7726	$134.77	$134.75	$134.80
Purchase #3	$15.72	3.112%	$16.2092	$16.21	$16.20	$16.20
Purchase #4	$70.72	11.511%	$78.8606	$78.86	$78.85	$78.90
Purchase #5	$81.83	8.776%	$89.0114	$89.01	$89.00	$89.00
Purchase #6	$169.59	9.867%	$186.3234	$186.32	$186.30	$186.30
Purchase #7	$189.45	7.505%	$203.6682	$203.67	$203.65	$203.70
7 purchase totals =	$688.28		$755.4410	$755.44	$755.35	$755.50