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	$158.90	3.516%	$164.4869	$164.49	$164.50	$164.50
Purchase #2	$79.25	12.151%	$88.8797	$88.88	$88.90	$88.90
Purchase #3	$100.88	12.282%	$113.2701	$113.27	$113.25	$113.30
Purchase #4	$150.80	12.701%	$169.9531	$169.95	$169.95	$170.00
Purchase #5	$78.74	13.681%	$89.5124	$89.51	$89.50	$89.50
Purchase #6	$146.46	11.632%	$163.4962	$163.50	$163.50	$163.50
Purchase #7	$244.28	13.295%	$276.757	$276.76	$276.75	$276.80
7 purchase totals =	$959.31		$1,066.3554	$1,066.36	$1,066.35	$1,066.50