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	$47.57	6.684%	$50.7496	$50.75	$50.75	$50.70
Purchase #2	$242.66	8.835%	$264.099	$264.10	$264.10	$264.10
Purchase #3	$158.28	3.578%	$163.9433	$163.94	$163.95	$163.90
Purchase #4	$90.97	13.773%	$103.4993	$103.50	$103.50	$103.50
Purchase #5	$157.75	7.494%	$169.5718	$169.57	$169.55	$169.60
Purchase #6	$156.43	6.396%	$166.4353	$166.44	$166.45	$166.40
Purchase #7	$134.82	6.289%	$143.2988	$143.30	$143.30	$143.30
7 purchase totals =	$988.48		$1,061.5971	$1,061.60	$1,061.60	$1,061.50