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	$195.99	13.505%	$222.4584	$222.46	$222.45	$222.50
Purchase #2	$14.74	7.723%	$15.8784	$15.88	$15.90	$15.90
Purchase #3	$94.85	8.648%	$103.0526	$103.05	$103.05	$103.10
Purchase #4	$153.41	13.777%	$174.5453	$174.55	$174.55	$174.50
Purchase #5	$185.41	13.704%	$210.8186	$210.82	$210.80	$210.80
Purchase #6	$115.96	11.158%	$128.8988	$128.90	$128.90	$128.90
Purchase #7	$134.45	9.735%	$147.5387	$147.54	$147.55	$147.50
7 purchase totals =	$894.81		$1,003.1908	$1,003.20	$1,003.20	$1,003.20