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	$104.45	5.867%	$110.5781	$110.58	$110.60	$110.60
Purchase #2	$122.44	3.277%	$126.4524	$126.45	$126.45	$126.50
Purchase #3	$46.77	7.147%	$50.1127	$50.11	$50.10	$50.10
Purchase #4	$54.53	4.390%	$56.9239	$56.92	$56.90	$56.90
Purchase #5	$176.85	4.854%	$185.4343	$185.43	$185.45	$185.40
Purchase #6	$178.35	10.324%	$196.7629	$196.76	$196.75	$196.80
Purchase #7	$154.94	8.175%	$167.6063	$167.61	$167.60	$167.60
7 purchase totals =	$838.33		$893.8706	$893.86	$893.85	$893.90