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	$96.60	6.435%	$102.8162	$102.82	$102.80	$102.80
Purchase #2	$57.90	6.405%	$61.6085	$61.61	$61.60	$61.60
Purchase #3	$228.56	10.833%	$253.3199	$253.32	$253.30	$253.30
Purchase #4	$223.82	4.414%	$233.6994	$233.70	$233.70	$233.70
Purchase #5	$200.87	11.315%	$223.5984	$223.60	$223.60	$223.60
Purchase #6	$91.69	7.604%	$98.6621	$98.66	$98.65	$98.70
Purchase #7	$143.32	10.782%	$158.7728	$158.77	$158.75	$158.80
7 purchase totals =	$1,042.76		$1,132.4773	$1,132.48	$1,132.40	$1,132.50