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	$121.82	4.257%	$127.0059	$127.01	$127.00	$127.00
Purchase #2	$6.54	13.355%	$7.4134	$7.41	$7.40	$7.40
Purchase #3	$112.60	7.271%	$120.7871	$120.79	$120.80	$120.80
Purchase #4	$184.50	5.412%	$194.4851	$194.49	$194.50	$194.50
Purchase #5	$55.34	10.545%	$61.1756	$61.18	$61.20	$61.20
Purchase #6	$88.37	3.260%	$91.2509	$91.25	$91.25	$91.30
Purchase #7	$99.39	11.565%	$110.8845	$110.88	$110.90	$110.90
7 purchase totals =	$668.56		$713.0025	$713.01	$713.05	$713.10