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	$240.91	9.394%	$263.5411	$263.54	$263.55	$263.50
Purchase #2	$49.27	12.463%	$55.4105	$55.41	$55.40	$55.40
Purchase #3	$59.90	4.622%	$62.6686	$62.67	$62.65	$62.70
Purchase #4	$215.44	4.449%	$225.0249	$225.02	$225.00	$225.00
Purchase #5	$84.55	5.274%	$89.0092	$89.01	$89.00	$89.00
Purchase #6	$159.52	6.406%	$169.7389	$169.74	$169.75	$169.70
Purchase #7	$168.97	10.426%	$186.5868	$186.59	$186.60	$186.60
7 purchase totals =	$978.56		$1,051.9800	$1,051.98	$1,051.95	$1,051.90