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	$146.49	12.327%	$164.5478	$164.55	$164.55	$164.50
Purchase #2	$79.56	13.550%	$90.3404	$90.34	$90.35	$90.30
Purchase #3	$88.52	9.599%	$97.017	$97.02	$97.00	$97.00
Purchase #4	$127.92	7.454%	$137.4552	$137.46	$137.45	$137.50
Purchase #5	$250.72	12.516%	$282.1001	$282.10	$282.10	$282.10
Purchase #6	$188.54	11.865%	$210.9103	$210.91	$210.90	$210.90
Purchase #7	$203.92	4.241%	$212.5682	$212.57	$212.55	$212.60
7 purchase totals =	$1,085.67		$1,194.9390	$1,194.95	$1,194.90	$1,194.90