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	$65.75	5.500%	$69.3663	$69.37	$69.35	$69.40
Purchase #2	$186.47	7.700%	$200.8282	$200.83	$200.85	$200.80
Purchase #3	$55.59	7.191%	$59.5875	$59.59	$59.60	$59.60
Purchase #4	$141.83	4.824%	$148.6719	$148.67	$148.65	$148.70
Purchase #5	$196.51	5.265%	$206.8563	$206.86	$206.85	$206.90
Purchase #6	$222.61	4.784%	$233.2597	$233.26	$233.25	$233.30
Purchase #7	$159.27	7.767%	$171.6405	$171.64	$171.65	$171.60
7 purchase totals =	$1,028.03		$1,090.2104	$1,090.22	$1,090.20	$1,090.30