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	$185.41	5.781%	$196.1286	$196.13	$196.15	$196.10
Purchase #2	$62.98	11.379%	$70.1465	$70.15	$70.15	$70.10
Purchase #3	$64.71	3.382%	$66.8985	$66.90	$66.90	$66.90
Purchase #4	$153.47	4.226%	$159.9556	$159.96	$159.95	$160.00
Purchase #5	$232.63	13.213%	$263.3674	$263.37	$263.35	$263.40
Purchase #6	$196.40	3.729%	$203.7238	$203.72	$203.70	$203.70
Purchase #7	$47.89	7.692%	$51.5737	$51.57	$51.55	$51.60
7 purchase totals =	$943.49		$1,011.7941	$1,011.80	$1,011.75	$1,011.80