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	$166.50	3.688%	$172.6405	$172.64	$172.65	$172.60
Purchase #2	$223.47	4.307%	$233.0949	$233.09	$233.10	$233.10
Purchase #3	$92.25	12.405%	$103.6936	$103.69	$103.70	$103.70
Purchase #4	$93.67	12.115%	$105.0181	$105.02	$105.00	$105.00
Purchase #5	$159.38	7.596%	$171.4865	$171.49	$171.50	$171.50
Purchase #6	$92.31	12.127%	$103.5044	$103.50	$103.50	$103.50
Purchase #7	$143.58	11.645%	$160.2999	$160.30	$160.30	$160.30
7 purchase totals =	$971.16		$1,049.7379	$1,049.73	$1,049.75	$1,049.70