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	$119.98	11.700%	$134.0177	$134.02	$134.00	$134.00
Purchase #2	$157.46	11.345%	$175.3238	$175.32	$175.30	$175.30
Purchase #3	$224.78	6.275%	$238.8849	$238.88	$238.90	$238.90
Purchase #4	$99.99	11.840%	$111.8288	$111.83	$111.85	$111.80
Purchase #5	$64.42	11.584%	$71.8824	$71.88	$71.90	$71.90
Purchase #6	$212.69	9.510%	$232.9168	$232.92	$232.90	$232.90
Purchase #7	$187.49	13.742%	$213.2549	$213.25	$213.25	$213.30
7 purchase totals =	$1,066.81		$1,178.1093	$1,178.10	$1,178.10	$1,178.10