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	$162.42	12.412%	$182.5796	$182.58	$182.60	$182.60
Purchase #2	$159.27	3.183%	$164.3396	$164.34	$164.35	$164.30
Purchase #3	$239.57	7.490%	$257.5138	$257.51	$257.50	$257.50
Purchase #4	$193.25	8.428%	$209.5371	$209.54	$209.55	$209.50
Purchase #5	$113.55	5.298%	$119.5659	$119.57	$119.55	$119.60
Purchase #6	$78.87	13.393%	$89.4331	$89.43	$89.45	$89.40
Purchase #7	$73.72	9.433%	$80.674	$80.67	$80.65	$80.70
7 purchase totals =	$1,020.65		$1,103.6431	$1,103.64	$1,103.65	$1,103.60