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	$187.71	9.199%	$204.9774	$204.98	$205.00	$205.00
Purchase #2	$38.46	13.402%	$43.6144	$43.61	$43.60	$43.60
Purchase #3	$23.33	6.543%	$24.8565	$24.86	$24.85	$24.90
Purchase #4	$20.84	7.438%	$22.3901	$22.39	$22.40	$22.40
Purchase #5	$85.64	5.334%	$90.208	$90.21	$90.20	$90.20
Purchase #6	$154.56	8.735%	$168.0608	$168.06	$168.05	$168.10
Purchase #7	$226.82	3.788%	$235.4119	$235.41	$235.40	$235.40
7 purchase totals =	$737.36		$789.5191	$789.52	$789.50	$789.60