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	$159.37	6.250%	$169.3306	$169.33	$169.35	$169.30
Purchase #2	$201.33	4.507%	$210.4039	$210.40	$210.40	$210.40
Purchase #3	$33.40	12.459%	$37.5613	$37.56	$37.55	$37.60
Purchase #4	$105.92	5.155%	$111.3802	$111.38	$111.40	$111.40
Purchase #5	$31.37	7.257%	$33.6465	$33.65	$33.65	$33.60
Purchase #6	$112.95	13.845%	$128.5879	$128.59	$128.60	$128.60
Purchase #7	$39.67	5.731%	$41.9435	$41.94	$41.95	$41.90
7 purchase totals =	$684.01		$732.8539	$732.85	$732.90	$732.80