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	$233.32	9.316%	$255.0561	$255.06	$255.05	$255.10
Purchase #2	$245.56	11.399%	$273.5514	$273.55	$273.55	$273.60
Purchase #3	$108.29	7.729%	$116.6597	$116.66	$116.65	$116.70
Purchase #4	$96.94	7.852%	$104.5517	$104.55	$104.55	$104.60
Purchase #5	$38.94	13.417%	$44.1646	$44.16	$44.15	$44.20
Purchase #6	$30.33	6.734%	$32.3724	$32.37	$32.35	$32.40
Purchase #7	$196.46	13.300%	$222.5892	$222.59	$222.60	$222.60
7 purchase totals =	$949.84		$1,048.9451	$1,048.94	$1,048.90	$1,049.20