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	$43.97	9.802%	$48.2799	$48.28	$48.30	$48.30
Purchase #2	$238.82	5.701%	$252.4351	$252.44	$252.45	$252.40
Purchase #3	$117.36	3.112%	$121.0122	$121.01	$121.00	$121.00
Purchase #4	$158.65	12.404%	$178.3289	$178.33	$178.35	$178.30
Purchase #5	$159.61	7.534%	$171.635	$171.64	$171.65	$171.60
Purchase #6	$98.83	6.767%	$105.5178	$105.52	$105.50	$105.50
Purchase #7	$171.64	7.527%	$184.5593	$184.56	$184.55	$184.60
7 purchase totals =	$988.88		$1,061.7682	$1,061.78	$1,061.80	$1,061.70