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	$211.40	8.564%	$229.5043	$229.50	$229.50	$229.50
Purchase #2	$102.75	7.294%	$110.2446	$110.24	$110.25	$110.20
Purchase #3	$218.49	10.277%	$240.9442	$240.94	$240.95	$240.90
Purchase #4	$111.38	11.429%	$124.1096	$124.11	$124.10	$124.10
Purchase #5	$90.80	8.769%	$98.7623	$98.76	$98.75	$98.80
Purchase #6	$94.33	6.627%	$100.5812	$100.58	$100.60	$100.60
Purchase #7	$133.46	7.244%	$143.1278	$143.13	$143.15	$143.10
7 purchase totals =	$962.61		$1,047.2740	$1,047.26	$1,047.30	$1,047.20