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	$83.75	12.605%	$94.3067	$94.31	$94.30	$94.30
Purchase #2	$191.82	12.663%	$216.1102	$216.11	$216.10	$216.10
Purchase #3	$31.52	13.326%	$35.7204	$35.72	$35.70	$35.70
Purchase #4	$245.89	13.859%	$279.9679	$279.97	$279.95	$280.00
Purchase #5	$153.41	9.509%	$167.9978	$168.00	$168.00	$168.00
Purchase #6	$68.98	3.836%	$71.6261	$71.63	$71.65	$71.60
Purchase #7	$125.69	4.402%	$131.2229	$131.22	$131.20	$131.20
7 purchase totals =	$901.06		$996.9520	$996.96	$996.90	$996.90