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	$172.51	12.722%	$194.4567	$194.46	$194.45	$194.50
Purchase #2	$104.55	5.792%	$110.6055	$110.61	$110.60	$110.60
Purchase #3	$161.66	3.849%	$167.8823	$167.88	$167.90	$167.90
Purchase #4	$24.98	10.752%	$27.6658	$27.67	$27.65	$27.70
Purchase #5	$232.35	10.369%	$256.4424	$256.44	$256.45	$256.40
Purchase #6	$245.72	7.771%	$264.8149	$264.81	$264.80	$264.80
Purchase #7	$68.98	5.748%	$72.945	$72.95	$72.95	$72.90
7 purchase totals =	$1,010.75		$1,094.8126	$1,094.82	$1,094.80	$1,094.80