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	$73.80	6.635%	$78.6966	$78.70	$78.70	$78.70
Purchase #2	$136.68	12.581%	$153.8757	$153.88	$153.90	$153.90
Purchase #3	$212.39	7.136%	$227.5462	$227.55	$227.55	$227.50
Purchase #4	$44.69	8.241%	$48.3729	$48.37	$48.35	$48.40
Purchase #5	$128.41	7.168%	$137.6144	$137.61	$137.60	$137.60
Purchase #6	$192.27	12.147%	$215.625	$215.63	$215.65	$215.60
Purchase #7	$214.53	13.558%	$243.616	$243.62	$243.60	$243.60
7 purchase totals =	$1,002.77		$1,105.3468	$1,105.36	$1,105.35	$1,105.30