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	$26.32	8.663%	$28.6001	$28.60	$28.60	$28.60
Purchase #2	$164.75	12.403%	$185.1839	$185.18	$185.20	$185.20
Purchase #3	$198.29	6.547%	$211.272	$211.27	$211.25	$211.30
Purchase #4	$187.69	4.468%	$196.076	$196.08	$196.10	$196.10
Purchase #5	$233.80	3.629%	$242.2846	$242.28	$242.30	$242.30
Purchase #6	$216.51	13.663%	$246.0918	$246.09	$246.10	$246.10
Purchase #7	$165.67	4.351%	$172.8783	$172.88	$172.90	$172.90
7 purchase totals =	$1,193.03		$1,282.3867	$1,282.38	$1,282.45	$1,282.50