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	$49.27	11.865%	$55.1159	$55.12	$55.10	$55.10
Purchase #2	$154.48	9.108%	$168.55	$168.55	$168.55	$168.60
Purchase #3	$159.42	3.808%	$165.4907	$165.49	$165.50	$165.50
Purchase #4	$168.77	12.755%	$190.2966	$190.30	$190.30	$190.30
Purchase #5	$48.95	5.681%	$51.7308	$51.73	$51.75	$51.70
Purchase #6	$209.28	8.426%	$226.9139	$226.91	$226.90	$226.90
Purchase #7	$95.51	9.323%	$104.4144	$104.41	$104.40	$104.40
7 purchase totals =	$885.68		$962.5123	$962.51	$962.50	$962.50