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	$42.34	5.654%	$44.7339	$44.73	$44.75	$44.70
Purchase #2	$123.97	5.333%	$130.5813	$130.58	$130.60	$130.60
Purchase #3	$104.32	4.718%	$109.2418	$109.24	$109.25	$109.20
Purchase #4	$105.70	12.723%	$119.1482	$119.15	$119.15	$119.10
Purchase #5	$190.37	3.186%	$196.4352	$196.44	$196.45	$196.40
Purchase #6	$228.53	11.406%	$254.5961	$254.60	$254.60	$254.60
Purchase #7	$232.87	9.715%	$255.4933	$255.49	$255.50	$255.50
7 purchase totals =	$1,028.10		$1,110.2298	$1,110.23	$1,110.30	$1,110.10