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	$130.41	10.673%	$144.3287	$144.33	$144.35	$144.30
Purchase #2	$150.30	10.750%	$166.4573	$166.46	$166.45	$166.50
Purchase #3	$97.46	6.845%	$104.1311	$104.13	$104.15	$104.10
Purchase #4	$75.84	3.627%	$78.5907	$78.59	$78.60	$78.60
Purchase #5	$172.53	10.701%	$190.9924	$190.99	$191.00	$191.00
Purchase #6	$166.75	7.780%	$179.7232	$179.72	$179.70	$179.70
Purchase #7	$134.69	4.869%	$141.2481	$141.25	$141.25	$141.20
7 purchase totals =	$927.98		$1,005.4715	$1,005.47	$1,005.50	$1,005.40