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	$191.83	3.514%	$198.5709	$198.57	$198.55	$198.60
Purchase #2	$148.83	13.588%	$169.053	$169.05	$169.05	$169.10
Purchase #3	$81.92	9.501%	$89.7032	$89.70	$89.70	$89.70
Purchase #4	$162.58	9.509%	$178.0397	$178.04	$178.05	$178.00
Purchase #5	$120.32	9.201%	$131.3906	$131.39	$131.40	$131.40
Purchase #6	$228.59	13.548%	$259.5594	$259.56	$259.55	$259.60
Purchase #7	$79.64	13.541%	$90.4241	$90.42	$90.40	$90.40
7 purchase totals =	$1,013.71		$1,116.7409	$1,116.73	$1,116.70	$1,116.80