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	$53.64	5.648%	$56.6696	$56.67	$56.65	$56.70
Purchase #2	$187.44	12.547%	$210.9581	$210.96	$210.95	$211.00
Purchase #3	$234.86	8.466%	$254.7432	$254.74	$254.75	$254.70
Purchase #4	$218.64	13.363%	$247.8569	$247.86	$247.85	$247.90
Purchase #5	$179.34	4.601%	$187.5914	$187.59	$187.60	$187.60
Purchase #6	$41.41	9.208%	$45.223	$45.22	$45.20	$45.20
Purchase #7	$123.49	3.158%	$127.3898	$127.39	$127.40	$127.40
7 purchase totals =	$1,038.82		$1,130.4320	$1,130.43	$1,130.40	$1,130.50