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	$32.85	3.166%	$33.89	$33.89	$33.90	$33.90
Purchase #2	$132.68	13.284%	$150.3052	$150.31	$150.30	$150.30
Purchase #3	$45.70	11.370%	$50.8961	$50.90	$50.90	$50.90
Purchase #4	$175.82	9.661%	$192.806	$192.81	$192.80	$192.80
Purchase #5	$195.53	9.171%	$213.4621	$213.46	$213.45	$213.50
Purchase #6	$190.69	13.148%	$215.7619	$215.76	$215.75	$215.80
Purchase #7	$154.53	9.301%	$168.9028	$168.90	$168.90	$168.90
7 purchase totals =	$927.80		$1,026.0241	$1,026.03	$1,026.00	$1,026.10