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	$174.62	3.341%	$180.4541	$180.45	$180.45	$180.50
Purchase #2	$102.48	9.146%	$111.8528	$111.85	$111.85	$111.90
Purchase #3	$97.38	3.167%	$100.464	$100.46	$100.45	$100.50
Purchase #4	$17.69	7.302%	$18.9817	$18.98	$19.00	$19.00
Purchase #5	$139.94	5.684%	$147.8942	$147.89	$147.90	$147.90
Purchase #6	$248.84	6.608%	$265.2833	$265.28	$265.30	$265.30
Purchase #7	$48.72	4.681%	$51.0006	$51.00	$51.00	$51.00
7 purchase totals =	$829.67		$875.9307	$875.91	$875.95	$876.10