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	$99.60	3.360%	$102.9466	$102.95	$102.95	$102.90
Purchase #2	$184.56	3.439%	$190.907	$190.91	$190.90	$190.90
Purchase #3	$245.33	4.215%	$255.6707	$255.67	$255.65	$255.70
Purchase #4	$74.78	5.196%	$78.6656	$78.67	$78.65	$78.70
Purchase #5	$189.56	11.573%	$211.4978	$211.50	$211.50	$211.50
Purchase #6	$147.66	4.147%	$153.7835	$153.78	$153.80	$153.80
Purchase #7	$141.28	3.870%	$146.7475	$146.75	$146.75	$146.70
7 purchase totals =	$1,082.77		$1,140.2187	$1,140.23	$1,140.20	$1,140.20