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	$80.93	8.333%	$87.6739	$87.67	$87.65	$87.70
Purchase #2	$171.78	8.802%	$186.9001	$186.90	$186.90	$186.90
Purchase #3	$156.76	11.281%	$174.4441	$174.44	$174.45	$174.40
Purchase #4	$151.86	13.548%	$172.434	$172.43	$172.45	$172.40
Purchase #5	$160.43	3.223%	$165.6007	$165.60	$165.60	$165.60
Purchase #6	$116.81	10.450%	$129.0166	$129.02	$129.00	$129.00
Purchase #7	$131.27	5.478%	$138.461	$138.46	$138.45	$138.50
7 purchase totals =	$969.84		$1,054.5304	$1,054.52	$1,054.50	$1,054.50