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	$185.52	6.131%	$196.8942	$196.89	$196.90	$196.90
Purchase #2	$83.89	7.750%	$90.3915	$90.39	$90.40	$90.40
Purchase #3	$187.33	11.543%	$208.9535	$208.95	$208.95	$209.00
Purchase #4	$180.68	13.359%	$204.817	$204.82	$204.80	$204.80
Purchase #5	$132.61	3.736%	$137.5643	$137.56	$137.55	$137.60
Purchase #6	$132.38	5.802%	$140.0607	$140.06	$140.05	$140.10
Purchase #7	$226.31	5.514%	$238.7887	$238.79	$238.80	$238.80
7 purchase totals =	$1,128.72		$1,217.4699	$1,217.46	$1,217.45	$1,217.60