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	$98.65	5.190%	$103.7699	$103.77	$103.75	$103.80
Purchase #2	$192.90	12.573%	$217.1533	$217.15	$217.15	$217.20
Purchase #3	$34.25	3.438%	$35.4275	$35.43	$35.45	$35.40
Purchase #4	$116.88	12.404%	$131.3778	$131.38	$131.40	$131.40
Purchase #5	$26.29	8.803%	$28.6043	$28.60	$28.60	$28.60
Purchase #6	$220.90	13.344%	$250.3769	$250.38	$250.40	$250.40
Purchase #7	$249.47	3.676%	$258.6405	$258.64	$258.65	$258.60
7 purchase totals =	$939.34		$1,025.3502	$1,025.35	$1,025.40	$1,025.40