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	$167.42	3.588%	$173.427	$173.43	$173.45	$173.40
Purchase #2	$86.72	3.729%	$89.9538	$89.95	$89.95	$90.00
Purchase #3	$133.85	13.136%	$151.4325	$151.43	$151.45	$151.40
Purchase #4	$88.63	7.619%	$95.3827	$95.38	$95.40	$95.40
Purchase #5	$104.33	11.273%	$116.0911	$116.09	$116.10	$116.10
Purchase #6	$244.50	6.646%	$260.7495	$260.75	$260.75	$260.70
Purchase #7	$35.71	6.496%	$38.0297	$38.03	$38.05	$38.00
7 purchase totals =	$861.16		$925.0663	$925.06	$925.15	$925.00