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	$51.98	5.662%	$54.9231	$54.92	$54.90	$54.90
Purchase #2	$148.50	5.191%	$156.2086	$156.21	$156.20	$156.20
Purchase #3	$63.89	10.578%	$70.6483	$70.65	$70.65	$70.60
Purchase #4	$239.97	13.776%	$273.0283	$273.03	$273.05	$273.00
Purchase #5	$188.27	6.244%	$200.0256	$200.03	$200.05	$200.00
Purchase #6	$92.61	4.486%	$96.7645	$96.76	$96.75	$96.80
Purchase #7	$112.27	12.610%	$126.4272	$126.43	$126.45	$126.40
7 purchase totals =	$897.49		$978.0256	$978.03	$978.05	$977.90