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	$157.26	13.801%	$178.9635	$178.96	$178.95	$179.00
Purchase #2	$94.32	5.245%	$99.2671	$99.27	$99.25	$99.30
Purchase #3	$216.80	6.718%	$231.3646	$231.36	$231.35	$231.40
Purchase #4	$38.34	11.369%	$42.6989	$42.70	$42.70	$42.70
Purchase #5	$146.45	5.143%	$153.9819	$153.98	$154.00	$154.00
Purchase #6	$47.26	12.221%	$53.0356	$53.04	$53.05	$53.00
Purchase #7	$205.72	13.503%	$233.4984	$233.50	$233.50	$233.50
7 purchase totals =	$906.15		$992.8100	$992.81	$992.80	$992.90