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	$55.55	11.220%	$61.7827	$61.78	$61.80	$61.80
Purchase #2	$39.51	7.433%	$42.4468	$42.45	$42.45	$42.40
Purchase #3	$185.63	5.596%	$196.0179	$196.02	$196.00	$196.00
Purchase #4	$19.84	10.661%	$21.9551	$21.96	$21.95	$22.00
Purchase #5	$42.80	6.389%	$45.5345	$45.53	$45.55	$45.50
Purchase #6	$157.43	8.857%	$171.3736	$171.37	$171.35	$171.40
Purchase #7	$185.65	11.293%	$206.6155	$206.62	$206.60	$206.60
7 purchase totals =	$686.41		$745.7261	$745.73	$745.70	$745.70