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	$196.94	5.753%	$208.27	$208.27	$208.25	$208.30
Purchase #2	$120.83	6.340%	$128.4906	$128.49	$128.50	$128.50
Purchase #3	$184.80	6.281%	$196.4073	$196.41	$196.40	$196.40
Purchase #4	$207.46	11.456%	$231.2266	$231.23	$231.25	$231.20
Purchase #5	$186.85	6.775%	$199.5091	$199.51	$199.50	$199.50
Purchase #6	$122.27	4.665%	$127.9739	$127.97	$127.95	$128.00
Purchase #7	$233.26	6.473%	$248.3589	$248.36	$248.35	$248.40
7 purchase totals =	$1,252.41		$1,340.2364	$1,340.24	$1,340.20	$1,340.30