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	$175.65	5.277%	$184.9191	$184.92	$184.90	$184.90
Purchase #2	$169.59	11.811%	$189.6203	$189.62	$189.60	$189.60
Purchase #3	$17.57	4.547%	$18.3689	$18.37	$18.35	$18.40
Purchase #4	$73.55	9.390%	$80.4563	$80.46	$80.45	$80.50
Purchase #5	$157.72	13.776%	$179.4475	$179.45	$179.45	$179.40
Purchase #6	$222.47	5.838%	$235.4578	$235.46	$235.45	$235.50
Purchase #7	$98.80	13.120%	$111.7626	$111.76	$111.75	$111.80
7 purchase totals =	$915.35		$1,000.0325	$1,000.04	$999.95	$1,000.10