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	$185.55	5.749%	$196.2173	$196.22	$196.20	$196.20
Purchase #2	$245.63	3.258%	$253.6326	$253.63	$253.65	$253.60
Purchase #3	$161.71	13.302%	$183.2207	$183.22	$183.20	$183.20
Purchase #4	$232.52	11.597%	$259.4853	$259.49	$259.50	$259.50
Purchase #5	$52.25	7.454%	$56.1447	$56.14	$56.15	$56.10
Purchase #6	$103.40	9.852%	$113.587	$113.59	$113.60	$113.60
Purchase #7	$34.36	4.221%	$35.8103	$35.81	$35.80	$35.80
7 purchase totals =	$1,015.42		$1,098.0979	$1,098.10	$1,098.10	$1,098.00