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	$194.56	5.760%	$205.7667	$205.77	$205.75	$205.80
Purchase #2	$160.96	4.257%	$167.8121	$167.81	$167.80	$167.80
Purchase #3	$97.51	13.514%	$110.6875	$110.69	$110.70	$110.70
Purchase #4	$62.86	12.703%	$70.8451	$70.85	$70.85	$70.80
Purchase #5	$175.91	4.823%	$184.3941	$184.39	$184.40	$184.40
Purchase #6	$134.67	12.525%	$151.5374	$151.54	$151.55	$151.50
Purchase #7	$222.37	12.547%	$250.2708	$250.27	$250.25	$250.30
7 purchase totals =	$1,048.84		$1,141.3137	$1,141.32	$1,141.30	$1,141.30