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	$199.37	11.697%	$222.6903	$222.69	$222.70	$222.70
Purchase #2	$48.57	3.202%	$50.1252	$50.13	$50.15	$50.10
Purchase #3	$51.62	4.538%	$53.9625	$53.96	$53.95	$54.00
Purchase #4	$200.96	11.811%	$224.6954	$224.70	$224.70	$224.70
Purchase #5	$218.52	6.815%	$233.4121	$233.41	$233.40	$233.40
Purchase #6	$183.84	4.176%	$191.5172	$191.52	$191.50	$191.50
Purchase #7	$53.47	12.148%	$59.9655	$59.97	$59.95	$60.00
7 purchase totals =	$956.35		$1,036.3682	$1,036.38	$1,036.35	$1,036.40