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	$173.42	10.429%	$191.506	$191.51	$191.50	$191.50
Purchase #2	$206.50	9.725%	$226.5821	$226.58	$226.60	$226.60
Purchase #3	$179.73	3.349%	$185.7492	$185.75	$185.75	$185.70
Purchase #4	$55.81	13.472%	$63.3287	$63.33	$63.35	$63.30
Purchase #5	$205.39	7.375%	$220.5375	$220.54	$220.55	$220.50
Purchase #6	$149.32	4.162%	$155.5347	$155.53	$155.55	$155.50
Purchase #7	$96.41	3.614%	$99.8943	$99.89	$99.90	$99.90
7 purchase totals =	$1,066.58		$1,143.1325	$1,143.13	$1,143.20	$1,143.00