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	$79.45	11.169%	$88.3238	$88.32	$88.30	$88.30
Purchase #2	$182.48	9.117%	$199.1167	$199.12	$199.10	$199.10
Purchase #3	$11.88	9.111%	$12.9624	$12.96	$12.95	$13.00
Purchase #4	$176.63	4.844%	$185.186	$185.19	$185.20	$185.20
Purchase #5	$206.48	5.431%	$217.6939	$217.69	$217.70	$217.70
Purchase #6	$91.59	4.687%	$95.8828	$95.88	$95.90	$95.90
Purchase #7	$199.52	11.564%	$222.5925	$222.59	$222.60	$222.60
7 purchase totals =	$948.03		$1,021.7581	$1,021.75	$1,021.75	$1,021.80