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	$171.88	10.673%	$190.2248	$190.22	$190.20	$190.20
Purchase #2	$69.58	6.154%	$73.862	$73.86	$73.85	$73.90
Purchase #3	$150.88	11.669%	$168.4862	$168.49	$168.50	$168.50
Purchase #4	$100.56	11.655%	$112.2803	$112.28	$112.30	$112.30
Purchase #5	$53.80	13.554%	$61.0921	$61.09	$61.10	$61.10
Purchase #6	$68.65	4.870%	$71.9933	$71.99	$72.00	$72.00
Purchase #7	$58.58	5.873%	$62.0204	$62.02	$62.00	$62.00
7 purchase totals =	$673.93		$739.9591	$739.95	$739.95	$740.00