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	$62.64	11.526%	$69.8599	$69.86	$69.85	$69.90
Purchase #2	$208.67	7.223%	$223.7422	$223.74	$223.75	$223.70
Purchase #3	$85.94	5.740%	$90.873	$90.87	$90.85	$90.90
Purchase #4	$35.94	9.251%	$39.2648	$39.26	$39.25	$39.30
Purchase #5	$112.42	3.372%	$116.2108	$116.21	$116.20	$116.20
Purchase #6	$23.56	7.858%	$25.4113	$25.41	$25.40	$25.40
Purchase #7	$103.60	4.508%	$108.2703	$108.27	$108.25	$108.30
7 purchase totals =	$632.77		$673.6323	$673.62	$673.55	$673.70