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	$168.61	13.207%	$190.8783	$190.88	$190.90	$190.90
Purchase #2	$187.26	13.461%	$212.4671	$212.47	$212.45	$212.50
Purchase #3	$19.59	9.121%	$21.3768	$21.38	$21.40	$21.40
Purchase #4	$13.68	6.128%	$14.5183	$14.52	$14.50	$14.50
Purchase #5	$243.94	8.828%	$265.475	$265.48	$265.50	$265.50
Purchase #6	$216.47	9.533%	$237.1061	$237.11	$237.10	$237.10
Purchase #7	$142.50	11.520%	$158.916	$158.92	$158.90	$158.90
7 purchase totals =	$992.05		$1,100.7376	$1,100.76	$1,100.75	$1,100.80