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	$46.34	10.849%	$51.3674	$51.37	$51.35	$51.40
Purchase #2	$172.31	11.629%	$192.3479	$192.35	$192.35	$192.30
Purchase #3	$203.96	9.296%	$222.9201	$222.92	$222.90	$222.90
Purchase #4	$172.79	9.162%	$188.621	$188.62	$188.60	$188.60
Purchase #5	$159.91	13.745%	$181.8896	$181.89	$181.90	$181.90
Purchase #6	$72.94	12.873%	$82.3296	$82.33	$82.35	$82.30
Purchase #7	$185.87	5.758%	$196.5724	$196.57	$196.55	$196.60
7 purchase totals =	$1,014.12		$1,116.0480	$1,116.05	$1,116.00	$1,116.00