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	$146.99	4.401%	$153.459	$153.46	$153.45	$153.50
Purchase #2	$201.76	13.783%	$229.5686	$229.57	$229.55	$229.60
Purchase #3	$201.93	10.437%	$223.0054	$223.01	$223.00	$223.00
Purchase #4	$230.81	10.665%	$255.4259	$255.43	$255.45	$255.40
Purchase #5	$81.94	9.117%	$89.4105	$89.41	$89.40	$89.40
Purchase #6	$204.74	11.127%	$227.5214	$227.52	$227.50	$227.50
Purchase #7	$237.44	11.499%	$264.7432	$264.74	$264.75	$264.70
7 purchase totals =	$1,305.61		$1,443.1340	$1,443.14	$1,443.10	$1,443.10