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	$237.78	10.725%	$263.2819	$263.28	$263.30	$263.30
Purchase #2	$200.48	12.473%	$225.4859	$225.49	$225.50	$225.50
Purchase #3	$95.46	4.630%	$99.8798	$99.88	$99.90	$99.90
Purchase #4	$45.75	10.413%	$50.5139	$50.51	$50.50	$50.50
Purchase #5	$35.65	4.127%	$37.1213	$37.12	$37.10	$37.10
Purchase #6	$19.25	6.793%	$20.5577	$20.56	$20.55	$20.60
Purchase #7	$70.64	10.737%	$78.2246	$78.22	$78.20	$78.20
7 purchase totals =	$705.01		$775.0651	$775.06	$775.05	$775.10