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	$119.64	9.420%	$130.9101	$130.91	$130.90	$130.90
Purchase #2	$147.88	12.659%	$166.6001	$166.60	$166.60	$166.60
Purchase #3	$28.36	9.124%	$30.9476	$30.95	$30.95	$30.90
Purchase #4	$81.70	9.145%	$89.1715	$89.17	$89.15	$89.20
Purchase #5	$132.91	12.127%	$149.028	$149.03	$149.05	$149.00
Purchase #6	$112.34	6.482%	$119.6219	$119.62	$119.60	$119.60
Purchase #7	$67.70	6.826%	$72.3212	$72.32	$72.30	$72.30
7 purchase totals =	$690.53		$758.6004	$758.60	$758.55	$758.50