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	$212.54	4.260%	$221.5942	$221.59	$221.60	$221.60
Purchase #2	$97.52	10.828%	$108.0795	$108.08	$108.10	$108.10
Purchase #3	$87.60	3.691%	$90.8333	$90.83	$90.85	$90.80
Purchase #4	$236.39	8.274%	$255.9489	$255.95	$255.95	$255.90
Purchase #5	$73.36	4.617%	$76.747	$76.75	$76.75	$76.70
Purchase #6	$165.44	4.667%	$173.1611	$173.16	$173.15	$173.20
Purchase #7	$164.66	4.234%	$171.6317	$171.63	$171.65	$171.60
7 purchase totals =	$1,037.51		$1,097.9957	$1,097.99	$1,098.05	$1,097.90