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	$111.29	7.745%	$119.9094	$119.91	$119.90	$119.90
Purchase #2	$173.78	6.421%	$184.9384	$184.94	$184.95	$184.90
Purchase #3	$99.82	11.702%	$111.5009	$111.50	$111.50	$111.50
Purchase #4	$154.36	4.786%	$161.7477	$161.75	$161.75	$161.70
Purchase #5	$160.99	4.130%	$167.6389	$167.64	$167.65	$167.60
Purchase #6	$163.72	12.131%	$183.5809	$183.58	$183.60	$183.60
Purchase #7	$174.30	3.178%	$179.8393	$179.84	$179.85	$179.80
7 purchase totals =	$1,038.26		$1,109.1555	$1,109.16	$1,109.20	$1,109.00