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	$112.42	11.633%	$125.4978	$125.50	$125.50	$125.50
Purchase #2	$68.31	8.150%	$73.8773	$73.88	$73.90	$73.90
Purchase #3	$200.72	11.121%	$223.0421	$223.04	$223.05	$223.00
Purchase #4	$244.66	12.238%	$274.6015	$274.60	$274.60	$274.60
Purchase #5	$213.69	11.552%	$238.3755	$238.38	$238.40	$238.40
Purchase #6	$241.59	13.716%	$274.7265	$274.73	$274.75	$274.70
Purchase #7	$53.76	10.371%	$59.3354	$59.34	$59.35	$59.30
7 purchase totals =	$1,135.15		$1,269.4561	$1,269.47	$1,269.55	$1,269.40