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	$87.38	4.392%	$91.2177	$91.22	$91.20	$91.20
Purchase #2	$40.64	10.140%	$44.7609	$44.76	$44.75	$44.80
Purchase #3	$200.59	4.263%	$209.1412	$209.14	$209.15	$209.10
Purchase #4	$59.31	13.641%	$67.4005	$67.40	$67.40	$67.40
Purchase #5	$249.36	4.847%	$261.4465	$261.45	$261.45	$261.40
Purchase #6	$109.57	12.792%	$123.5862	$123.59	$123.60	$123.60
Purchase #7	$9.93	12.604%	$11.1816	$11.18	$11.20	$11.20
7 purchase totals =	$756.78		$808.7346	$808.74	$808.75	$808.70