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	$176.92	4.131%	$184.2286	$184.23	$184.25	$184.20
Purchase #2	$50.67	6.727%	$54.0786	$54.08	$54.10	$54.10
Purchase #3	$47.47	12.490%	$53.399	$53.40	$53.40	$53.40
Purchase #4	$22.64	6.546%	$24.122	$24.12	$24.10	$24.10
Purchase #5	$62.69	12.482%	$70.515	$70.52	$70.50	$70.50
Purchase #6	$191.60	4.683%	$200.5726	$200.57	$200.55	$200.60
Purchase #7	$195.44	3.871%	$203.0055	$203.01	$203.00	$203.00
7 purchase totals =	$747.43		$789.9213	$789.93	$789.90	$789.90