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	$118.90	11.761%	$132.8838	$132.88	$132.90	$132.90
Purchase #2	$90.87	10.400%	$100.3205	$100.32	$100.30	$100.30
Purchase #3	$233.90	9.610%	$256.3778	$256.38	$256.40	$256.40
Purchase #4	$214.80	4.499%	$224.4639	$224.46	$224.45	$224.50
Purchase #5	$93.58	3.769%	$97.107	$97.11	$97.10	$97.10
Purchase #6	$113.55	6.304%	$120.7082	$120.71	$120.70	$120.70
Purchase #7	$99.57	13.215%	$112.7282	$112.73	$112.75	$112.70
7 purchase totals =	$965.17		$1,044.5894	$1,044.59	$1,044.60	$1,044.60