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	$40.73	9.570%	$44.6279	$44.63	$44.65	$44.60
Purchase #2	$31.41	12.694%	$35.3972	$35.40	$35.40	$35.40
Purchase #3	$239.79	6.171%	$254.5874	$254.59	$254.60	$254.60
Purchase #4	$246.83	10.512%	$272.7768	$272.78	$272.80	$272.80
Purchase #5	$41.45	9.389%	$45.3417	$45.34	$45.35	$45.30
Purchase #6	$179.56	11.567%	$200.3297	$200.33	$200.35	$200.30
Purchase #7	$214.98	12.728%	$242.3427	$242.34	$242.35	$242.30
7 purchase totals =	$994.75		$1,095.4034	$1,095.41	$1,095.50	$1,095.30