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	$165.31	3.637%	$171.3223	$171.32	$171.30	$171.30
Purchase #2	$155.72	4.577%	$162.8473	$162.85	$162.85	$162.80
Purchase #3	$224.86	5.671%	$237.6118	$237.61	$237.60	$237.60
Purchase #4	$55.83	3.545%	$57.8092	$57.81	$57.80	$57.80
Purchase #5	$154.62	8.423%	$167.6436	$167.64	$167.65	$167.60
Purchase #6	$244.44	13.363%	$277.1045	$277.10	$277.10	$277.10
Purchase #7	$117.52	7.696%	$126.5643	$126.56	$126.55	$126.60
7 purchase totals =	$1,118.30		$1,200.9030	$1,200.89	$1,200.85	$1,200.80