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	$232.92	8.629%	$253.0187	$253.02	$253.00	$253.00
Purchase #2	$179.62	4.435%	$187.5861	$187.59	$187.60	$187.60
Purchase #3	$180.39	4.704%	$188.8755	$188.88	$188.90	$188.90
Purchase #4	$234.43	10.273%	$258.513	$258.51	$258.50	$258.50
Purchase #5	$78.50	13.322%	$88.9578	$88.96	$88.95	$89.00
Purchase #6	$83.35	3.710%	$86.4423	$86.44	$86.45	$86.40
Purchase #7	$8.27	3.786%	$8.5831	$8.58	$8.60	$8.60
7 purchase totals =	$997.48		$1,071.9765	$1,071.98	$1,072.00	$1,072.00