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	$181.29	9.557%	$198.6159	$198.62	$198.60	$198.60
Purchase #2	$124.27	10.771%	$137.6551	$137.66	$137.65	$137.70
Purchase #3	$31.48	6.754%	$33.6062	$33.61	$33.60	$33.60
Purchase #4	$154.98	10.565%	$171.3536	$171.35	$171.35	$171.40
Purchase #5	$94.95	11.224%	$105.6072	$105.61	$105.60	$105.60
Purchase #6	$92.37	6.809%	$98.6595	$98.66	$98.65	$98.70
Purchase #7	$187.30	8.633%	$203.4696	$203.47	$203.45	$203.50
7 purchase totals =	$866.64		$948.9671	$948.98	$948.90	$949.10