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	$197.34	6.529%	$210.2243	$210.22	$210.20	$210.20
Purchase #2	$86.44	4.720%	$90.52	$90.52	$90.50	$90.50
Purchase #3	$124.88	3.675%	$129.4693	$129.47	$129.45	$129.50
Purchase #4	$28.97	5.204%	$30.4776	$30.48	$30.50	$30.50
Purchase #5	$107.77	3.357%	$111.3878	$111.39	$111.40	$111.40
Purchase #6	$159.96	3.429%	$165.445	$165.45	$165.45	$165.40
Purchase #7	$228.51	4.308%	$238.3542	$238.35	$238.35	$238.40
7 purchase totals =	$933.87		$975.8782	$975.88	$975.85	$975.90