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	$26.41	4.580%	$27.6196	$27.62	$27.60	$27.60
Purchase #2	$159.58	3.338%	$164.9068	$164.91	$164.90	$164.90
Purchase #3	$94.27	10.162%	$103.8497	$103.85	$103.85	$103.80
Purchase #4	$132.72	9.706%	$145.6018	$145.60	$145.60	$145.60
Purchase #5	$61.96	3.498%	$64.1274	$64.13	$64.15	$64.10
Purchase #6	$117.91	9.855%	$129.53	$129.53	$129.55	$129.50
Purchase #7	$182.94	4.225%	$190.6692	$190.67	$190.65	$190.70
7 purchase totals =	$775.79		$826.3045	$826.31	$826.30	$826.20