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	$103.86	10.263%	$114.5192	$114.52	$114.50	$114.50
Purchase #2	$5.49	10.387%	$6.0602	$6.06	$6.05	$6.10
Purchase #3	$83.85	10.836%	$92.936	$92.94	$92.95	$92.90
Purchase #4	$233.28	3.220%	$240.7916	$240.79	$240.80	$240.80
Purchase #5	$36.32	6.713%	$38.7582	$38.76	$38.75	$38.80
Purchase #6	$186.57	3.210%	$192.5589	$192.56	$192.55	$192.60
Purchase #7	$83.72	8.547%	$90.8755	$90.88	$90.90	$90.90
7 purchase totals =	$733.09		$776.4996	$776.51	$776.50	$776.60