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	$94.89	7.329%	$101.8445	$101.84	$101.85	$101.80
Purchase #2	$105.55	11.816%	$118.0218	$118.02	$118.00	$118.00
Purchase #3	$156.69	9.755%	$171.9751	$171.98	$172.00	$172.00
Purchase #4	$234.71	5.726%	$248.1495	$248.15	$248.15	$248.10
Purchase #5	$56.95	9.782%	$62.5208	$62.52	$62.50	$62.50
Purchase #6	$215.28	7.584%	$231.6068	$231.61	$231.60	$231.60
Purchase #7	$137.34	13.312%	$155.6227	$155.62	$155.60	$155.60
7 purchase totals =	$1,001.41		$1,089.7412	$1,089.74	$1,089.70	$1,089.60