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	$100.48	4.664%	$105.1664	$105.17	$105.15	$105.20
Purchase #2	$92.60	13.257%	$104.876	$104.88	$104.90	$104.90
Purchase #3	$110.80	8.540%	$120.2623	$120.26	$120.25	$120.30
Purchase #4	$210.35	3.430%	$217.565	$217.57	$217.55	$217.60
Purchase #5	$229.90	4.635%	$240.5559	$240.56	$240.55	$240.60
Purchase #6	$68.96	13.226%	$78.0806	$78.08	$78.10	$78.10
Purchase #7	$216.91	10.225%	$239.089	$239.09	$239.10	$239.10
7 purchase totals =	$1,030.00		$1,105.5952	$1,105.61	$1,105.60	$1,105.80