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	$189.70	13.346%	$215.0174	$215.02	$215.00	$215.00
Purchase #2	$57.88	6.576%	$61.6862	$61.69	$61.70	$61.70
Purchase #3	$148.85	12.605%	$167.6125	$167.61	$167.60	$167.60
Purchase #4	$120.36	9.294%	$131.5463	$131.55	$131.55	$131.50
Purchase #5	$211.66	5.136%	$222.5309	$222.53	$222.55	$222.50
Purchase #6	$237.82	11.119%	$264.2632	$264.26	$264.25	$264.30
Purchase #7	$105.77	12.109%	$118.5777	$118.58	$118.60	$118.60
7 purchase totals =	$1,072.04		$1,181.2342	$1,181.24	$1,181.25	$1,181.20