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	$204.35	7.379%	$219.429	$219.43	$219.45	$219.40
Purchase #2	$76.74	5.475%	$80.9415	$80.94	$80.95	$80.90
Purchase #3	$65.64	10.202%	$72.3366	$72.34	$72.35	$72.30
Purchase #4	$154.62	11.783%	$172.8389	$172.84	$172.85	$172.80
Purchase #5	$88.66	6.471%	$94.3972	$94.40	$94.40	$94.40
Purchase #6	$159.80	5.283%	$168.2422	$168.24	$168.25	$168.20
Purchase #7	$63.91	5.712%	$67.5605	$67.56	$67.55	$67.60
7 purchase totals =	$813.72		$875.7459	$875.75	$875.80	$875.60