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	$169.35	9.665%	$185.7177	$185.72	$185.70	$185.70
Purchase #2	$247.86	13.312%	$280.8551	$280.86	$280.85	$280.90
Purchase #3	$43.71	13.278%	$49.5138	$49.51	$49.50	$49.50
Purchase #4	$83.27	3.666%	$86.3227	$86.32	$86.30	$86.30
Purchase #5	$232.89	13.639%	$264.6539	$264.65	$264.65	$264.70
Purchase #6	$189.26	10.282%	$208.7197	$208.72	$208.70	$208.70
Purchase #7	$136.82	6.478%	$145.6832	$145.68	$145.70	$145.70
7 purchase totals =	$1,103.16		$1,221.4661	$1,221.46	$1,221.40	$1,221.50