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	$187.59	11.724%	$209.5831	$209.58	$209.60	$209.60
Purchase #2	$32.26	10.476%	$35.6396	$35.64	$35.65	$35.60
Purchase #3	$96.61	10.645%	$106.8941	$106.89	$106.90	$106.90
Purchase #4	$154.48	13.866%	$175.9002	$175.90	$175.90	$175.90
Purchase #5	$140.90	13.658%	$160.1441	$160.14	$160.15	$160.10
Purchase #6	$194.83	13.752%	$221.623	$221.62	$221.60	$221.60
Purchase #7	$98.76	5.505%	$104.1967	$104.20	$104.20	$104.20
7 purchase totals =	$905.43		$1,013.9808	$1,013.97	$1,014.00	$1,013.90