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	$95.83	7.348%	$102.8716	$102.87	$102.85	$102.90
Purchase #2	$51.99	8.543%	$56.4315	$56.43	$56.45	$56.40
Purchase #3	$189.76	5.460%	$200.1209	$200.12	$200.10	$200.10
Purchase #4	$52.38	10.862%	$58.0695	$58.07	$58.05	$58.10
Purchase #5	$201.95	3.576%	$209.1717	$209.17	$209.15	$209.20
Purchase #6	$145.72	8.681%	$158.37	$158.37	$158.35	$158.40
Purchase #7	$52.69	13.501%	$59.8037	$59.80	$59.80	$59.80
7 purchase totals =	$790.32		$844.8389	$844.83	$844.75	$844.90