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	$142.66	6.357%	$151.7289	$151.73	$151.75	$151.70
Purchase #2	$105.39	6.789%	$112.5449	$112.54	$112.55	$112.50
Purchase #3	$212.87	9.785%	$233.6993	$233.70	$233.70	$233.70
Purchase #4	$85.44	13.276%	$96.783	$96.78	$96.80	$96.80
Purchase #5	$15.50	13.162%	$17.5401	$17.54	$17.55	$17.50
Purchase #6	$168.76	6.675%	$180.0247	$180.02	$180.00	$180.00
Purchase #7	$208.97	7.833%	$225.3386	$225.34	$225.35	$225.30
7 purchase totals =	$939.59		$1,017.6595	$1,017.65	$1,017.70	$1,017.50