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	$41.26	4.728%	$43.2108	$43.21	$43.20	$43.20
Purchase #2	$93.68	3.107%	$96.5906	$96.59	$96.60	$96.60
Purchase #3	$40.53	6.802%	$43.2869	$43.29	$43.30	$43.30
Purchase #4	$240.68	10.106%	$265.0031	$265.00	$265.00	$265.00
Purchase #5	$201.57	8.859%	$219.4271	$219.43	$219.45	$219.40
Purchase #6	$40.68	11.788%	$45.4754	$45.48	$45.50	$45.50
Purchase #7	$147.87	11.223%	$164.4655	$164.47	$164.45	$164.50
7 purchase totals =	$806.27		$877.4594	$877.47	$877.50	$877.50