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	$107.92	9.631%	$118.3138	$118.31	$118.30	$118.30
Purchase #2	$38.87	9.627%	$42.612	$42.61	$42.60	$42.60
Purchase #3	$45.88	8.842%	$49.9367	$49.94	$49.95	$49.90
Purchase #4	$241.27	5.417%	$254.3396	$254.34	$254.35	$254.30
Purchase #5	$198.64	8.617%	$215.7568	$215.76	$215.75	$215.80
Purchase #6	$90.27	8.671%	$98.0973	$98.10	$98.10	$98.10
Purchase #7	$240.59	12.437%	$270.5122	$270.51	$270.50	$270.50
7 purchase totals =	$963.44		$1,049.5684	$1,049.57	$1,049.55	$1,049.50