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	$198.82	3.156%	$205.0948	$205.09	$205.10	$205.10
Purchase #2	$162.68	3.818%	$168.8911	$168.89	$168.90	$168.90
Purchase #3	$49.59	8.872%	$53.9896	$53.99	$54.00	$54.00
Purchase #4	$67.28	6.478%	$71.6384	$71.64	$71.65	$71.60
Purchase #5	$182.54	4.425%	$190.6174	$190.62	$190.60	$190.60
Purchase #6	$41.64	8.222%	$45.0636	$45.06	$45.05	$45.10
Purchase #7	$90.75	7.617%	$97.6624	$97.66	$97.65	$97.70
7 purchase totals =	$793.30		$832.9573	$832.95	$832.95	$833.00