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	$47.30	13.466%	$53.6694	$53.67	$53.65	$53.70
Purchase #2	$154.66	9.227%	$168.9305	$168.93	$168.95	$168.90
Purchase #3	$141.84	12.871%	$160.0962	$160.10	$160.10	$160.10
Purchase #4	$235.32	13.241%	$266.4787	$266.48	$266.50	$266.50
Purchase #5	$153.75	8.472%	$166.7757	$166.78	$166.80	$166.80
Purchase #6	$55.44	7.715%	$59.7172	$59.72	$59.70	$59.70
Purchase #7	$167.45	13.187%	$189.5316	$189.53	$189.55	$189.50
7 purchase totals =	$955.76		$1,065.1993	$1,065.21	$1,065.25	$1,065.20