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	$132.52	7.353%	$142.2642	$142.26	$142.25	$142.30
Purchase #2	$53.39	10.497%	$58.9943	$58.99	$59.00	$59.00
Purchase #3	$229.42	4.850%	$240.5469	$240.55	$240.55	$240.50
Purchase #4	$96.26	3.506%	$99.6349	$99.63	$99.65	$99.60
Purchase #5	$42.67	7.646%	$45.9325	$45.93	$45.95	$45.90
Purchase #6	$213.58	5.869%	$226.115	$226.12	$226.10	$226.10
Purchase #7	$34.51	8.712%	$37.5165	$37.52	$37.50	$37.50
7 purchase totals =	$802.35		$851.0043	$851.00	$851.00	$850.90