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	$58.56	7.550%	$62.9813	$62.98	$63.00	$63.00
Purchase #2	$68.91	5.794%	$72.9026	$72.90	$72.90	$72.90
Purchase #3	$139.90	8.711%	$152.0867	$152.09	$152.10	$152.10
Purchase #4	$134.44	13.331%	$152.3622	$152.36	$152.35	$152.40
Purchase #5	$214.85	12.732%	$242.2047	$242.20	$242.20	$242.20
Purchase #6	$52.87	6.584%	$56.351	$56.35	$56.35	$56.40
Purchase #7	$182.67	7.497%	$196.3648	$196.36	$196.35	$196.40
7 purchase totals =	$852.20		$935.2533	$935.24	$935.25	$935.40