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	$247.64	3.551%	$256.4337	$256.43	$256.45	$256.40
Purchase #2	$241.67	3.540%	$250.2251	$250.23	$250.25	$250.20
Purchase #3	$100.76	6.628%	$107.4384	$107.44	$107.45	$107.40
Purchase #4	$127.49	4.860%	$133.686	$133.69	$133.70	$133.70
Purchase #5	$49.91	8.129%	$53.9672	$53.97	$53.95	$54.00
Purchase #6	$27.54	13.329%	$31.2108	$31.21	$31.20	$31.20
Purchase #7	$199.54	11.567%	$222.6208	$222.62	$222.60	$222.60
7 purchase totals =	$994.55		$1,055.5820	$1,055.59	$1,055.60	$1,055.50