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	$227.35	4.790%	$238.2401	$238.24	$238.25	$238.20
Purchase #2	$175.94	7.110%	$188.4493	$188.45	$188.45	$188.40
Purchase #3	$212.88	5.214%	$223.9796	$223.98	$224.00	$224.00
Purchase #4	$99.42	11.851%	$111.2023	$111.20	$111.20	$111.20
Purchase #5	$107.45	8.394%	$116.4694	$116.47	$116.45	$116.50
Purchase #6	$148.78	12.846%	$167.8923	$167.89	$167.90	$167.90
Purchase #7	$109.61	12.849%	$123.6938	$123.69	$123.70	$123.70
7 purchase totals =	$1,081.43		$1,169.9268	$1,169.92	$1,169.95	$1,169.90