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	$142.99	6.506%	$152.2929	$152.29	$152.30	$152.30
Purchase #2	$174.38	12.623%	$196.392	$196.39	$196.40	$196.40
Purchase #3	$162.92	12.633%	$183.5017	$183.50	$183.50	$183.50
Purchase #4	$56.26	12.847%	$63.4877	$63.49	$63.50	$63.50
Purchase #5	$111.39	10.408%	$122.9835	$122.98	$123.00	$123.00
Purchase #6	$160.43	7.377%	$172.2649	$172.26	$172.25	$172.30
Purchase #7	$190.75	9.114%	$208.135	$208.14	$208.15	$208.10
7 purchase totals =	$999.12		$1,099.0577	$1,099.05	$1,099.10	$1,099.10