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	$235.27	7.796%	$253.6116	$253.61	$253.60	$253.60
Purchase #2	$185.74	5.741%	$196.4033	$196.40	$196.40	$196.40
Purchase #3	$168.50	7.380%	$180.9353	$180.94	$180.95	$180.90
Purchase #4	$36.28	9.735%	$39.8119	$39.81	$39.80	$39.80
Purchase #5	$65.82	10.858%	$72.9667	$72.97	$72.95	$73.00
Purchase #6	$60.69	7.178%	$65.0463	$65.05	$65.05	$65.00
Purchase #7	$45.56	9.422%	$49.8527	$49.85	$49.85	$49.90
7 purchase totals =	$797.86		$858.6278	$858.63	$858.60	$858.60