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	$68.46	12.562%	$77.0599	$77.06	$77.05	$77.10
Purchase #2	$159.83	4.683%	$167.3148	$167.31	$167.30	$167.30
Purchase #3	$209.93	3.660%	$217.6134	$217.61	$217.60	$217.60
Purchase #4	$238.82	3.730%	$247.728	$247.73	$247.75	$247.70
Purchase #5	$75.71	13.405%	$85.8589	$85.86	$85.85	$85.90
Purchase #6	$104.55	10.220%	$115.235	$115.24	$115.25	$115.20
Purchase #7	$19.31	11.484%	$21.5276	$21.53	$21.55	$21.50
7 purchase totals =	$876.61		$932.3376	$932.34	$932.35	$932.30