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	$12.82	6.368%	$13.6364	$13.64	$13.65	$13.60
Purchase #2	$86.33	12.241%	$96.8977	$96.90	$96.90	$96.90
Purchase #3	$135.59	12.826%	$152.9808	$152.98	$153.00	$153.00
Purchase #4	$35.34	5.375%	$37.2395	$37.24	$37.25	$37.20
Purchase #5	$157.51	3.148%	$162.4684	$162.47	$162.45	$162.50
Purchase #6	$157.85	3.157%	$162.8333	$162.83	$162.85	$162.80
Purchase #7	$126.41	9.292%	$138.156	$138.16	$138.15	$138.20
7 purchase totals =	$711.85		$764.2121	$764.22	$764.25	$764.20