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	$192.71	4.127%	$200.6631	$200.66	$200.65	$200.70
Purchase #2	$245.88	12.588%	$276.8314	$276.83	$276.85	$276.80
Purchase #3	$245.40	5.278%	$258.3522	$258.35	$258.35	$258.40
Purchase #4	$168.54	4.415%	$175.981	$175.98	$176.00	$176.00
Purchase #5	$31.96	11.389%	$35.5999	$35.60	$35.60	$35.60
Purchase #6	$132.77	13.460%	$150.6408	$150.64	$150.65	$150.60
Purchase #7	$56.61	4.540%	$59.1801	$59.18	$59.20	$59.20
7 purchase totals =	$1,073.87		$1,157.2485	$1,157.24	$1,157.30	$1,157.30