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	$112.51	5.810%	$119.0468	$119.05	$119.05	$119.00
Purchase #2	$77.77	11.265%	$86.5308	$86.53	$86.55	$86.50
Purchase #3	$136.27	5.770%	$144.1328	$144.13	$144.15	$144.10
Purchase #4	$250.82	11.707%	$280.1835	$280.18	$280.20	$280.20
Purchase #5	$219.50	8.475%	$238.1026	$238.10	$238.10	$238.10
Purchase #6	$237.87	8.473%	$258.0247	$258.02	$258.00	$258.00
Purchase #7	$73.58	13.485%	$83.5023	$83.50	$83.50	$83.50
7 purchase totals =	$1,108.32		$1,209.5235	$1,209.51	$1,209.55	$1,209.40