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	$183.71	9.723%	$201.5721	$201.57	$201.55	$201.60
Purchase #2	$210.60	5.704%	$222.6126	$222.61	$222.60	$222.60
Purchase #3	$38.85	10.427%	$42.9009	$42.90	$42.90	$42.90
Purchase #4	$92.58	5.195%	$97.3895	$97.39	$97.40	$97.40
Purchase #5	$27.82	4.616%	$29.1042	$29.10	$29.10	$29.10
Purchase #6	$59.28	7.272%	$63.5908	$63.59	$63.60	$63.60
Purchase #7	$78.91	4.371%	$82.3592	$82.36	$82.35	$82.40
7 purchase totals =	$691.75		$739.5293	$739.52	$739.50	$739.60