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	$220.52	10.346%	$243.335	$243.34	$243.35	$243.30
Purchase #2	$92.87	6.278%	$98.7004	$98.70	$98.70	$98.70
Purchase #3	$127.90	8.814%	$139.1731	$139.17	$139.15	$139.20
Purchase #4	$160.91	4.770%	$168.5854	$168.59	$168.60	$168.60
Purchase #5	$99.32	6.273%	$105.5503	$105.55	$105.55	$105.60
Purchase #6	$145.45	6.140%	$154.3806	$154.38	$154.40	$154.40
Purchase #7	$167.57	11.753%	$187.2645	$187.26	$187.25	$187.30
7 purchase totals =	$1,014.54		$1,096.9893	$1,096.99	$1,097.00	$1,097.10