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	$147.75	11.156%	$164.233	$164.23	$164.25	$164.20
Purchase #2	$238.99	6.769%	$255.1672	$255.17	$255.15	$255.20
Purchase #3	$59.45	3.137%	$61.3149	$61.31	$61.30	$61.30
Purchase #4	$24.34	6.530%	$25.9294	$25.93	$25.95	$25.90
Purchase #5	$207.59	5.286%	$218.5632	$218.56	$218.55	$218.60
Purchase #6	$18.73	9.390%	$20.4887	$20.49	$20.50	$20.50
Purchase #7	$235.38	6.611%	$250.941	$250.94	$250.95	$250.90
7 purchase totals =	$932.23		$996.6374	$996.63	$996.65	$996.60