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	$95.38	5.784%	$100.8968	$100.90	$100.90	$100.90
Purchase #2	$51.29	3.431%	$53.0498	$53.05	$53.05	$53.00
Purchase #3	$112.60	9.510%	$123.3083	$123.31	$123.30	$123.30
Purchase #4	$49.53	9.193%	$54.0833	$54.08	$54.10	$54.10
Purchase #5	$181.98	9.384%	$199.057	$199.06	$199.05	$199.10
Purchase #6	$242.95	11.332%	$270.4811	$270.48	$270.50	$270.50
Purchase #7	$111.64	10.450%	$123.3064	$123.31	$123.30	$123.30
7 purchase totals =	$845.37		$924.1827	$924.19	$924.20	$924.20