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	$197.40	3.855%	$205.0098	$205.01	$205.00	$205.00
Purchase #2	$178.49	12.102%	$200.0909	$200.09	$200.10	$200.10
Purchase #3	$30.33	7.255%	$32.5304	$32.53	$32.55	$32.50
Purchase #4	$225.36	4.415%	$235.3096	$235.31	$235.30	$235.30
Purchase #5	$18.47	10.156%	$20.3458	$20.35	$20.35	$20.30
Purchase #6	$31.43	12.826%	$35.4612	$35.46	$35.45	$35.50
Purchase #7	$40.87	10.505%	$45.1634	$45.16	$45.15	$45.20
7 purchase totals =	$722.35		$773.9111	$773.91	$773.90	$773.90