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	$98.62	3.458%	$102.0303	$102.03	$102.05	$102.00
Purchase #2	$221.73	12.825%	$250.1669	$250.17	$250.15	$250.20
Purchase #3	$65.28	11.734%	$72.94	$72.94	$72.95	$72.90
Purchase #4	$195.34	10.834%	$216.5031	$216.50	$216.50	$216.50
Purchase #5	$156.72	3.144%	$161.6473	$161.65	$161.65	$161.60
Purchase #6	$80.43	12.184%	$90.2296	$90.23	$90.25	$90.20
Purchase #7	$143.45	13.331%	$162.5733	$162.57	$162.55	$162.60
7 purchase totals =	$961.57		$1,056.0905	$1,056.09	$1,056.10	$1,056.00