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	$94.44	11.543%	$105.3412	$105.34	$105.35	$105.30
Purchase #2	$179.81	5.466%	$189.6384	$189.64	$189.65	$189.60
Purchase #3	$14.74	4.441%	$15.3946	$15.39	$15.40	$15.40
Purchase #4	$244.71	5.855%	$259.0378	$259.04	$259.05	$259.00
Purchase #5	$219.98	4.142%	$229.0916	$229.09	$229.10	$229.10
Purchase #6	$59.36	13.435%	$67.335	$67.34	$67.35	$67.30
Purchase #7	$73.37	7.381%	$78.7854	$78.79	$78.80	$78.80
7 purchase totals =	$886.41		$944.6240	$944.63	$944.70	$944.50