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	$241.41	13.526%	$274.0631	$274.06	$274.05	$274.10
Purchase #2	$102.81	6.557%	$109.5513	$109.55	$109.55	$109.60
Purchase #3	$27.59	3.661%	$28.6001	$28.60	$28.60	$28.60
Purchase #4	$127.73	12.771%	$144.0424	$144.04	$144.05	$144.00
Purchase #5	$229.98	5.671%	$243.0222	$243.02	$243.00	$243.00
Purchase #6	$52.88	3.676%	$54.8239	$54.82	$54.80	$54.80
Purchase #7	$35.25	13.467%	$39.9971	$40.00	$40.00	$40.00
7 purchase totals =	$817.65		$894.1001	$894.09	$894.05	$894.10