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	$159.94	7.170%	$171.4077	$171.41	$171.40	$171.40
Purchase #2	$136.50	13.254%	$154.5917	$154.59	$154.60	$154.60
Purchase #3	$10.29	11.660%	$11.4898	$11.49	$11.50	$11.50
Purchase #4	$122.98	6.599%	$131.0955	$131.10	$131.10	$131.10
Purchase #5	$57.47	3.560%	$59.5159	$59.52	$59.50	$59.50
Purchase #6	$119.95	11.740%	$134.0321	$134.03	$134.05	$134.00
Purchase #7	$216.27	12.450%	$243.1956	$243.20	$243.20	$243.20
7 purchase totals =	$823.40		$905.3283	$905.34	$905.35	$905.30