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	$131.29	11.639%	$146.5708	$146.57	$146.55	$146.60
Purchase #2	$115.71	3.463%	$119.717	$119.72	$119.70	$119.70
Purchase #3	$15.88	11.125%	$17.6467	$17.65	$17.65	$17.60
Purchase #4	$105.91	3.384%	$109.494	$109.49	$109.50	$109.50
Purchase #5	$79.52	3.597%	$82.3803	$82.38	$82.40	$82.40
Purchase #6	$170.69	8.192%	$184.6729	$184.67	$184.65	$184.70
Purchase #7	$70.51	10.637%	$78.0101	$78.01	$78.00	$78.00
7 purchase totals =	$689.51		$738.4918	$738.49	$738.45	$738.50