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	$135.32	12.341%	$152.0198	$152.02	$152.00	$152.00
Purchase #2	$62.48	4.433%	$65.2497	$65.25	$65.25	$65.20
Purchase #3	$85.46	12.710%	$96.322	$96.32	$96.30	$96.30
Purchase #4	$78.33	7.866%	$84.4914	$84.49	$84.50	$84.50
Purchase #5	$96.61	6.443%	$102.8346	$102.83	$102.85	$102.80
Purchase #6	$112.38	13.799%	$127.8873	$127.89	$127.90	$127.90
Purchase #7	$138.86	13.118%	$157.0757	$157.08	$157.10	$157.10
7 purchase totals =	$709.44		$785.8805	$785.88	$785.90	$785.80