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	$244.66	9.106%	$266.9387	$266.94	$266.95	$266.90
Purchase #2	$99.25	10.171%	$109.3447	$109.34	$109.35	$109.30
Purchase #3	$39.54	9.632%	$43.3485	$43.35	$43.35	$43.30
Purchase #4	$142.41	11.107%	$158.2275	$158.23	$158.25	$158.20
Purchase #5	$105.48	9.855%	$115.8751	$115.88	$115.90	$115.90
Purchase #6	$189.67	3.262%	$195.857	$195.86	$195.85	$195.90
Purchase #7	$118.53	7.312%	$127.1969	$127.20	$127.20	$127.20
7 purchase totals =	$939.54		$1,016.7884	$1,016.80	$1,016.85	$1,016.70