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	$52.73	13.607%	$59.905	$59.91	$59.90	$59.90
Purchase #2	$104.86	6.360%	$111.5291	$111.53	$111.55	$111.50
Purchase #3	$224.98	5.872%	$238.1908	$238.19	$238.20	$238.20
Purchase #4	$187.60	4.512%	$196.0645	$196.06	$196.05	$196.10
Purchase #5	$150.58	9.215%	$164.4559	$164.46	$164.45	$164.50
Purchase #6	$32.67	11.460%	$36.414	$36.41	$36.40	$36.40
Purchase #7	$124.50	4.427%	$130.0116	$130.01	$130.00	$130.00
7 purchase totals =	$877.92		$936.5709	$936.57	$936.55	$936.60