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	$217.63	5.113%	$228.7574	$228.76	$228.75	$228.80
Purchase #2	$36.42	5.842%	$38.5477	$38.55	$38.55	$38.50
Purchase #3	$45.93	11.159%	$51.0553	$51.06	$51.05	$51.10
Purchase #4	$135.69	3.249%	$140.0986	$140.10	$140.10	$140.10
Purchase #5	$148.42	13.428%	$168.3498	$168.35	$168.35	$168.30
Purchase #6	$243.57	6.713%	$259.9209	$259.92	$259.90	$259.90
Purchase #7	$246.47	11.778%	$275.4992	$275.50	$275.50	$275.50
7 purchase totals =	$1,074.13		$1,162.2289	$1,162.24	$1,162.20	$1,162.20