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	$221.77	7.405%	$238.1921	$238.19	$238.20	$238.20
Purchase #2	$12.32	5.642%	$13.0151	$13.02	$13.00	$13.00
Purchase #3	$112.50	3.473%	$116.4071	$116.41	$116.40	$116.40
Purchase #4	$190.44	9.369%	$208.2823	$208.28	$208.30	$208.30
Purchase #5	$216.69	5.324%	$228.2266	$228.23	$228.25	$228.20
Purchase #6	$128.27	11.115%	$142.5272	$142.53	$142.55	$142.50
Purchase #7	$136.93	10.166%	$150.8503	$150.85	$150.85	$150.90
7 purchase totals =	$1,018.92		$1,097.5007	$1,097.51	$1,097.55	$1,097.50