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	$82.61	9.728%	$90.6463	$90.65	$90.65	$90.60
Purchase #2	$179.56	7.117%	$192.3393	$192.34	$192.35	$192.30
Purchase #3	$189.51	10.224%	$208.8855	$208.89	$208.90	$208.90
Purchase #4	$239.25	11.435%	$266.6082	$266.61	$266.60	$266.60
Purchase #5	$150.25	6.295%	$159.7082	$159.71	$159.70	$159.70
Purchase #6	$112.26	4.608%	$117.4329	$117.43	$117.45	$117.40
Purchase #7	$225.50	3.644%	$233.7172	$233.72	$233.70	$233.70
7 purchase totals =	$1,178.94		$1,269.3376	$1,269.35	$1,269.35	$1,269.20