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	$69.34	13.167%	$78.47	$78.47	$78.45	$78.50
Purchase #2	$75.35	4.304%	$78.5931	$78.59	$78.60	$78.60
Purchase #3	$243.28	6.526%	$259.1565	$259.16	$259.15	$259.20
Purchase #4	$213.65	9.421%	$233.778	$233.78	$233.80	$233.80
Purchase #5	$213.61	7.333%	$229.274	$229.27	$229.25	$229.30
Purchase #6	$113.26	5.483%	$119.47	$119.47	$119.45	$119.50
Purchase #7	$193.38	9.431%	$211.6177	$211.62	$211.60	$211.60
7 purchase totals =	$1,121.87		$1,210.3593	$1,210.36	$1,210.30	$1,210.50