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	$146.85	3.587%	$152.1175	$152.12	$152.10	$152.10
Purchase #2	$85.83	3.228%	$88.6006	$88.60	$88.60	$88.60
Purchase #3	$19.89	3.361%	$20.5585	$20.56	$20.55	$20.60
Purchase #4	$20.60	8.540%	$22.3592	$22.36	$22.35	$22.40
Purchase #5	$63.94	8.667%	$69.4817	$69.48	$69.50	$69.50
Purchase #6	$43.65	8.846%	$47.5113	$47.51	$47.50	$47.50
Purchase #7	$58.40	5.807%	$61.7913	$61.79	$61.80	$61.80
7 purchase totals =	$439.16		$462.4201	$462.42	$462.40	$462.50