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	$140.67	7.859%	$151.7253	$151.73	$151.75	$151.70
Purchase #2	$66.81	8.185%	$72.2784	$72.28	$72.30	$72.30
Purchase #3	$168.53	4.664%	$176.3902	$176.39	$176.40	$176.40
Purchase #4	$114.33	7.817%	$123.2672	$123.27	$123.25	$123.30
Purchase #5	$179.87	4.467%	$187.9048	$187.90	$187.90	$187.90
Purchase #6	$207.68	12.757%	$234.1737	$234.17	$234.15	$234.20
Purchase #7	$241.89	9.619%	$265.1574	$265.16	$265.15	$265.20
7 purchase totals =	$1,119.78		$1,210.8970	$1,210.90	$1,210.90	$1,211.00