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	$233.84	8.661%	$254.0929	$254.09	$254.10	$254.10
Purchase #2	$89.85	12.824%	$101.3724	$101.37	$101.35	$101.40
Purchase #3	$80.50	11.129%	$89.4588	$89.46	$89.45	$89.50
Purchase #4	$81.99	11.789%	$91.6558	$91.66	$91.65	$91.70
Purchase #5	$220.35	3.685%	$228.4699	$228.47	$228.45	$228.50
Purchase #6	$169.40	3.381%	$175.1274	$175.13	$175.15	$175.10
Purchase #7	$160.67	9.838%	$176.4767	$176.48	$176.50	$176.50
7 purchase totals =	$1,036.60		$1,116.6539	$1,116.66	$1,116.65	$1,116.80