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	$169.90	12.147%	$190.5378	$190.54	$190.55	$190.50
Purchase #2	$181.59	13.674%	$206.4206	$206.42	$206.40	$206.40
Purchase #3	$67.54	7.695%	$72.7372	$72.74	$72.75	$72.70
Purchase #4	$124.77	8.639%	$135.5489	$135.55	$135.55	$135.50
Purchase #5	$247.47	13.518%	$280.923	$280.92	$280.90	$280.90
Purchase #6	$141.28	5.182%	$148.6011	$148.60	$148.60	$148.60
Purchase #7	$28.42	8.665%	$30.8826	$30.88	$30.90	$30.90
7 purchase totals =	$960.97		$1,065.6512	$1,065.65	$1,065.65	$1,065.50