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	$179.97	5.652%	$190.1419	$190.14	$190.15	$190.10
Purchase #2	$222.55	9.398%	$243.4652	$243.47	$243.45	$243.50
Purchase #3	$166.76	11.564%	$186.0441	$186.04	$186.05	$186.00
Purchase #4	$250.25	9.679%	$274.4717	$274.47	$274.45	$274.50
Purchase #5	$7.45	3.216%	$7.6896	$7.69	$7.70	$7.70
Purchase #6	$35.47	4.649%	$37.119	$37.12	$37.10	$37.10
Purchase #7	$210.45	7.302%	$225.8171	$225.82	$225.80	$225.80
7 purchase totals =	$1,072.90		$1,164.7486	$1,164.75	$1,164.70	$1,164.70