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	$191.26	12.620%	$215.397	$215.40	$215.40	$215.40
Purchase #2	$246.45	10.318%	$271.8787	$271.88	$271.90	$271.90
Purchase #3	$137.80	9.207%	$150.4872	$150.49	$150.50	$150.50
Purchase #4	$211.89	3.513%	$219.3337	$219.33	$219.35	$219.30
Purchase #5	$171.89	9.772%	$188.6871	$188.69	$188.70	$188.70
Purchase #6	$169.96	9.673%	$186.4002	$186.40	$186.40	$186.40
Purchase #7	$236.58	8.150%	$255.8613	$255.86	$255.85	$255.90
7 purchase totals =	$1,365.83		$1,488.0452	$1,488.05	$1,488.10	$1,488.10