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	$100.77	10.144%	$110.9921	$110.99	$111.00	$111.00
Purchase #2	$34.96	10.313%	$38.5654	$38.57	$38.55	$38.60
Purchase #3	$89.34	11.351%	$99.481	$99.48	$99.50	$99.50
Purchase #4	$227.51	10.486%	$251.3667	$251.37	$251.35	$251.40
Purchase #5	$126.55	13.364%	$143.4621	$143.46	$143.45	$143.50
Purchase #6	$108.66	3.470%	$112.4305	$112.43	$112.45	$112.40
Purchase #7	$245.84	7.139%	$263.3905	$263.39	$263.40	$263.40
7 purchase totals =	$933.63		$1,019.6883	$1,019.69	$1,019.70	$1,019.80