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	$192.98	5.104%	$202.8297	$202.83	$202.85	$202.80
Purchase #2	$119.50	3.674%	$123.8904	$123.89	$123.90	$123.90
Purchase #3	$224.82	8.224%	$243.3092	$243.31	$243.30	$243.30
Purchase #4	$215.85	8.381%	$233.9404	$233.94	$233.95	$233.90
Purchase #5	$37.99	11.266%	$42.27	$42.27	$42.25	$42.30
Purchase #6	$5.97	5.849%	$6.3192	$6.32	$6.30	$6.30
Purchase #7	$11.30	8.632%	$12.2754	$12.28	$12.30	$12.30
7 purchase totals =	$808.41		$864.8343	$864.84	$864.85	$864.80