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	$218.36	9.287%	$238.6391	$238.64	$238.65	$238.60
Purchase #2	$222.53	12.423%	$250.1749	$250.17	$250.15	$250.20
Purchase #3	$199.85	11.709%	$223.2504	$223.25	$223.25	$223.30
Purchase #4	$139.88	6.344%	$148.754	$148.75	$148.75	$148.80
Purchase #5	$19.82	6.692%	$21.1464	$21.15	$21.15	$21.10
Purchase #6	$173.75	10.321%	$191.6827	$191.68	$191.70	$191.70
Purchase #7	$14.98	8.492%	$16.2521	$16.25	$16.25	$16.30
7 purchase totals =	$989.17		$1,089.8996	$1,089.89	$1,089.90	$1,090.00