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	$57.29	4.222%	$59.7088	$59.71	$59.70	$59.70
Purchase #2	$183.84	8.440%	$199.3561	$199.36	$199.35	$199.40
Purchase #3	$13.31	3.392%	$13.7615	$13.76	$13.75	$13.80
Purchase #4	$139.84	6.483%	$148.9058	$148.91	$148.90	$148.90
Purchase #5	$155.30	3.107%	$160.1252	$160.13	$160.15	$160.10
Purchase #6	$25.73	10.642%	$28.4682	$28.47	$28.45	$28.50
Purchase #7	$36.54	12.426%	$41.0805	$41.08	$41.10	$41.10
7 purchase totals =	$611.85		$651.4061	$651.42	$651.40	$651.50