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	$224.54	9.280%	$245.3773	$245.38	$245.40	$245.40
Purchase #2	$83.32	7.379%	$89.4682	$89.47	$89.45	$89.50
Purchase #3	$121.35	7.221%	$130.1127	$130.11	$130.10	$130.10
Purchase #4	$131.64	6.444%	$140.1229	$140.12	$140.10	$140.10
Purchase #5	$133.55	6.679%	$142.4698	$142.47	$142.45	$142.50
Purchase #6	$99.94	8.430%	$108.3649	$108.36	$108.35	$108.40
Purchase #7	$153.30	11.345%	$170.6919	$170.69	$170.70	$170.70
7 purchase totals =	$947.64		$1,026.6077	$1,026.60	$1,026.55	$1,026.70