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	$244.91	7.214%	$262.5778	$262.58	$262.60	$262.60
Purchase #2	$73.85	11.677%	$82.4735	$82.47	$82.45	$82.50
Purchase #3	$247.99	6.566%	$264.273	$264.27	$264.25	$264.30
Purchase #4	$60.47	5.387%	$63.7275	$63.73	$63.75	$63.70
Purchase #5	$72.57	13.582%	$82.4265	$82.43	$82.45	$82.40
Purchase #6	$191.37	9.540%	$209.6267	$209.63	$209.65	$209.60
Purchase #7	$180.43	5.366%	$190.1119	$190.11	$190.10	$190.10
7 purchase totals =	$1,071.59		$1,155.2169	$1,155.22	$1,155.25	$1,155.20