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	$217.88	9.663%	$238.9337	$238.93	$238.95	$238.90
Purchase #2	$36.38	11.815%	$40.6783	$40.68	$40.70	$40.70
Purchase #3	$77.77	6.438%	$82.7768	$82.78	$82.80	$82.80
Purchase #4	$178.79	5.525%	$188.6681	$188.67	$188.65	$188.70
Purchase #5	$200.58	13.820%	$228.3002	$228.30	$228.30	$228.30
Purchase #6	$24.80	9.486%	$27.1525	$27.15	$27.15	$27.20
Purchase #7	$28.46	11.762%	$31.8075	$31.81	$31.80	$31.80
7 purchase totals =	$764.66		$838.3171	$838.32	$838.35	$838.40