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	$222.47	3.207%	$229.6046	$229.60	$229.60	$229.60
Purchase #2	$142.61	5.507%	$150.4635	$150.46	$150.45	$150.50
Purchase #3	$129.57	7.850%	$139.7412	$139.74	$139.75	$139.70
Purchase #4	$242.91	4.407%	$253.615	$253.62	$253.60	$253.60
Purchase #5	$172.26	7.131%	$184.5439	$184.54	$184.55	$184.50
Purchase #6	$34.44	3.152%	$35.5255	$35.53	$35.55	$35.50
Purchase #7	$20.94	10.322%	$23.1014	$23.10	$23.10	$23.10
7 purchase totals =	$965.20		$1,016.5951	$1,016.59	$1,016.60	$1,016.50