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	$191.79	11.868%	$214.5516	$214.55	$214.55	$214.60
Purchase #2	$99.87	11.151%	$111.0065	$111.01	$111.00	$111.00
Purchase #3	$129.94	8.705%	$141.2513	$141.25	$141.25	$141.30
Purchase #4	$165.31	8.130%	$178.7497	$178.75	$178.75	$178.70
Purchase #5	$199.90	7.831%	$215.5542	$215.55	$215.55	$215.60
Purchase #6	$89.75	3.784%	$93.1461	$93.15	$93.15	$93.10
Purchase #7	$79.71	11.672%	$89.0138	$89.01	$89.00	$89.00
7 purchase totals =	$956.27		$1,043.2732	$1,043.27	$1,043.25	$1,043.30