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	$33.97	7.212%	$36.4199	$36.42	$36.40	$36.40
Purchase #2	$71.54	6.421%	$76.1336	$76.13	$76.15	$76.10
Purchase #3	$219.58	6.254%	$233.3125	$233.31	$233.30	$233.30
Purchase #4	$63.93	5.405%	$67.3854	$67.39	$67.40	$67.40
Purchase #5	$91.75	10.609%	$101.4838	$101.48	$101.50	$101.50
Purchase #6	$36.59	6.419%	$38.9387	$38.94	$38.95	$38.90
Purchase #7	$41.64	13.720%	$47.353	$47.35	$47.35	$47.40
7 purchase totals =	$559.00		$601.0269	$601.02	$601.05	$601.00