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	$198.57	8.707%	$215.8595	$215.86	$215.85	$215.90
Purchase #2	$170.49	6.647%	$181.8225	$181.82	$181.80	$181.80
Purchase #3	$168.34	7.870%	$181.5884	$181.59	$181.60	$181.60
Purchase #4	$59.98	10.268%	$66.1387	$66.14	$66.15	$66.10
Purchase #5	$139.60	3.348%	$144.2738	$144.27	$144.25	$144.30
Purchase #6	$138.33	3.483%	$143.148	$143.15	$143.15	$143.10
Purchase #7	$200.80	4.319%	$209.4726	$209.47	$209.45	$209.50
7 purchase totals =	$1,076.11		$1,142.3035	$1,142.30	$1,142.25	$1,142.30