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	$131.65	12.331%	$147.8838	$147.88	$147.90	$147.90
Purchase #2	$187.82	3.709%	$194.7862	$194.79	$194.80	$194.80
Purchase #3	$18.52	3.824%	$19.2282	$19.23	$19.25	$19.20
Purchase #4	$126.48	12.803%	$142.6732	$142.67	$142.65	$142.70
Purchase #5	$116.93	8.857%	$127.2865	$127.29	$127.30	$127.30
Purchase #6	$148.32	3.460%	$153.4519	$153.45	$153.45	$153.50
Purchase #7	$86.91	13.351%	$98.5134	$98.51	$98.50	$98.50
7 purchase totals =	$816.63		$883.8232	$883.82	$883.85	$883.90