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	$247.67	4.429%	$258.6393	$258.64	$258.65	$258.60
Purchase #2	$101.95	5.269%	$107.3217	$107.32	$107.30	$107.30
Purchase #3	$153.83	8.382%	$166.724	$166.72	$166.70	$166.70
Purchase #4	$19.52	6.564%	$20.8013	$20.80	$20.80	$20.80
Purchase #5	$99.70	5.657%	$105.34	$105.34	$105.35	$105.30
Purchase #6	$133.36	9.708%	$146.3066	$146.31	$146.30	$146.30
Purchase #7	$210.51	5.738%	$222.5891	$222.59	$222.60	$222.60
7 purchase totals =	$966.54		$1,027.7220	$1,027.72	$1,027.70	$1,027.60