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	$82.31	8.590%	$89.3804	$89.38	$89.40	$89.40
Purchase #2	$13.28	9.268%	$14.5108	$14.51	$14.50	$14.50
Purchase #3	$168.69	8.725%	$183.4082	$183.41	$183.40	$183.40
Purchase #4	$216.44	12.291%	$243.0426	$243.04	$243.05	$243.00
Purchase #5	$185.45	12.726%	$209.0504	$209.05	$209.05	$209.10
Purchase #6	$235.26	7.767%	$253.5326	$253.53	$253.55	$253.50
Purchase #7	$67.74	5.777%	$71.6533	$71.65	$71.65	$71.70
7 purchase totals =	$969.17		$1,064.5783	$1,064.57	$1,064.60	$1,064.60