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	$205.42	13.456%	$233.0613	$233.06	$233.05	$233.10
Purchase #2	$166.75	8.292%	$180.5769	$180.58	$180.60	$180.60
Purchase #3	$39.65	6.873%	$42.3751	$42.38	$42.40	$42.40
Purchase #4	$240.47	9.805%	$264.0481	$264.05	$264.05	$264.00
Purchase #5	$171.76	4.564%	$179.5991	$179.60	$179.60	$179.60
Purchase #6	$31.75	11.228%	$35.3149	$35.31	$35.30	$35.30
Purchase #7	$98.80	10.283%	$108.9596	$108.96	$108.95	$109.00
7 purchase totals =	$954.60		$1,043.9350	$1,043.94	$1,043.95	$1,044.00