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	$75.92	8.209%	$82.1523	$82.15	$82.15	$82.20
Purchase #2	$248.28	10.691%	$274.8236	$274.82	$274.80	$274.80
Purchase #3	$176.65	10.169%	$194.6135	$194.61	$194.60	$194.60
Purchase #4	$21.73	6.561%	$23.1557	$23.16	$23.15	$23.20
Purchase #5	$151.36	9.256%	$165.3699	$165.37	$165.35	$165.40
Purchase #6	$95.41	10.554%	$105.4796	$105.48	$105.50	$105.50
Purchase #7	$217.51	9.586%	$238.3605	$238.36	$238.35	$238.40
7 purchase totals =	$986.86		$1,083.9551	$1,083.95	$1,083.90	$1,084.10