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	$125.50	4.649%	$131.3345	$131.33	$131.35	$131.30
Purchase #2	$41.49	12.208%	$46.5551	$46.56	$46.55	$46.60
Purchase #3	$92.88	8.319%	$100.6067	$100.61	$100.60	$100.60
Purchase #4	$120.93	8.611%	$131.3433	$131.34	$131.35	$131.30
Purchase #5	$165.90	3.872%	$172.3236	$172.32	$172.30	$172.30
Purchase #6	$20.41	7.565%	$21.954	$21.95	$21.95	$22.00
Purchase #7	$82.94	12.102%	$92.9774	$92.98	$93.00	$93.00
7 purchase totals =	$650.05		$697.0946	$697.09	$697.10	$697.10