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	$100.56	9.116%	$109.727	$109.73	$109.75	$109.70
Purchase #2	$108.77	5.323%	$114.5598	$114.56	$114.55	$114.60
Purchase #3	$30.85	6.634%	$32.8966	$32.90	$32.90	$32.90
Purchase #4	$149.67	5.741%	$158.2626	$158.26	$158.25	$158.30
Purchase #5	$40.55	9.322%	$44.3301	$44.33	$44.35	$44.30
Purchase #6	$201.89	12.104%	$226.3268	$226.33	$226.35	$226.30
Purchase #7	$156.91	5.359%	$165.3188	$165.32	$165.30	$165.30
7 purchase totals =	$789.20		$851.4217	$851.43	$851.45	$851.40