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	$238.73	9.199%	$260.6908	$260.69	$260.70	$260.70
Purchase #2	$85.44	7.783%	$92.0898	$92.09	$92.10	$92.10
Purchase #3	$46.34	5.520%	$48.898	$48.90	$48.90	$48.90
Purchase #4	$152.94	13.645%	$173.8087	$173.81	$173.80	$173.80
Purchase #5	$150.50	7.662%	$162.0313	$162.03	$162.05	$162.00
Purchase #6	$64.39	11.859%	$72.026	$72.03	$72.05	$72.00
Purchase #7	$180.86	5.831%	$191.4059	$191.41	$191.40	$191.40
7 purchase totals =	$919.20		$1,000.9505	$1,000.96	$1,001.00	$1,000.90