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	$233.88	12.228%	$262.4788	$262.48	$262.50	$262.50
Purchase #2	$59.59	11.642%	$66.5275	$66.53	$66.55	$66.50
Purchase #3	$199.56	11.322%	$222.1542	$222.15	$222.15	$222.20
Purchase #4	$109.39	8.187%	$118.3458	$118.35	$118.35	$118.30
Purchase #5	$137.34	9.304%	$150.1181	$150.12	$150.10	$150.10
Purchase #6	$103.51	5.845%	$109.5602	$109.56	$109.55	$109.60
Purchase #7	$194.87	5.579%	$205.7418	$205.74	$205.75	$205.70
7 purchase totals =	$1,038.14		$1,134.9264	$1,134.93	$1,134.95	$1,134.90