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	$92.34	11.637%	$103.0856	$103.09	$103.10	$103.10
Purchase #2	$41.75	3.457%	$43.1933	$43.19	$43.20	$43.20
Purchase #3	$19.67	8.469%	$21.3359	$21.34	$21.35	$21.30
Purchase #4	$175.75	8.776%	$191.1738	$191.17	$191.15	$191.20
Purchase #5	$168.90	10.663%	$186.9098	$186.91	$186.90	$186.90
Purchase #6	$64.77	11.779%	$72.3993	$72.40	$72.40	$72.40
Purchase #7	$154.94	8.814%	$168.5964	$168.60	$168.60	$168.60
7 purchase totals =	$718.12		$786.6941	$786.70	$786.70	$786.70