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	$134.75	5.740%	$142.4847	$142.48	$142.50	$142.50
Purchase #2	$143.80	7.194%	$154.145	$154.15	$154.15	$154.10
Purchase #3	$184.50	6.307%	$196.1364	$196.14	$196.15	$196.10
Purchase #4	$90.85	9.505%	$99.4853	$99.49	$99.50	$99.50
Purchase #5	$127.58	10.171%	$140.5562	$140.56	$140.55	$140.60
Purchase #6	$133.44	4.338%	$139.2286	$139.23	$139.25	$139.20
Purchase #7	$118.87	12.742%	$134.0164	$134.02	$134.00	$134.00
7 purchase totals =	$933.79		$1,006.0526	$1,006.07	$1,006.10	$1,006.00