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	$224.57	7.526%	$241.4711	$241.47	$241.45	$241.50
Purchase #2	$60.74	11.810%	$67.9134	$67.91	$67.90	$67.90
Purchase #3	$86.87	12.337%	$97.5872	$97.59	$97.60	$97.60
Purchase #4	$93.34	3.590%	$96.6909	$96.69	$96.70	$96.70
Purchase #5	$59.48	6.734%	$63.4854	$63.49	$63.50	$63.50
Purchase #6	$140.55	7.692%	$151.3611	$151.36	$151.35	$151.40
Purchase #7	$39.90	7.199%	$42.7724	$42.77	$42.75	$42.80
7 purchase totals =	$705.45		$761.2815	$761.28	$761.25	$761.40