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	$68.88	11.693%	$76.9341	$76.93	$76.95	$76.90
Purchase #2	$193.83	11.134%	$215.411	$215.41	$215.40	$215.40
Purchase #3	$137.30	4.740%	$143.808	$143.81	$143.80	$143.80
Purchase #4	$85.54	4.604%	$89.4783	$89.48	$89.50	$89.50
Purchase #5	$110.60	9.669%	$121.2939	$121.29	$121.30	$121.30
Purchase #6	$51.40	12.607%	$57.88	$57.88	$57.90	$57.90
Purchase #7	$191.26	7.404%	$205.4209	$205.42	$205.40	$205.40
7 purchase totals =	$838.81		$910.2262	$910.22	$910.25	$910.20