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	$40.54	11.351%	$45.1417	$45.14	$45.15	$45.10
Purchase #2	$233.30	11.349%	$259.7772	$259.78	$259.80	$259.80
Purchase #3	$228.97	4.408%	$239.063	$239.06	$239.05	$239.10
Purchase #4	$21.39	3.616%	$22.1635	$22.16	$22.15	$22.20
Purchase #5	$37.38	13.561%	$42.4491	$42.45	$42.45	$42.40
Purchase #6	$137.90	11.260%	$153.4275	$153.43	$153.45	$153.40
Purchase #7	$243.90	8.308%	$264.1632	$264.16	$264.15	$264.20
7 purchase totals =	$943.38		$1,026.1852	$1,026.18	$1,026.20	$1,026.20