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	$233.57	11.684%	$260.8603	$260.86	$260.85	$260.90
Purchase #2	$227.94	13.754%	$259.2909	$259.29	$259.30	$259.30
Purchase #3	$79.96	10.765%	$88.5677	$88.57	$88.55	$88.60
Purchase #4	$242.98	9.614%	$266.3401	$266.34	$266.35	$266.30
Purchase #5	$202.33	10.463%	$223.4998	$223.50	$223.50	$223.50
Purchase #6	$41.40	8.646%	$44.9794	$44.98	$45.00	$45.00
Purchase #7	$63.57	13.118%	$71.9091	$71.91	$71.90	$71.90
7 purchase totals =	$1,091.75		$1,215.4473	$1,215.45	$1,215.45	$1,215.50