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	$111.91	3.558%	$115.8918	$115.89	$115.90	$115.90
Purchase #2	$59.58	12.108%	$66.7939	$66.79	$66.80	$66.80
Purchase #3	$233.43	4.471%	$243.8667	$243.87	$243.85	$243.90
Purchase #4	$40.53	11.482%	$45.1837	$45.18	$45.20	$45.20
Purchase #5	$124.86	5.347%	$131.5363	$131.54	$131.55	$131.50
Purchase #6	$237.86	3.573%	$246.3587	$246.36	$246.35	$246.40
Purchase #7	$246.52	6.315%	$262.0877	$262.09	$262.10	$262.10
7 purchase totals =	$1,054.69		$1,111.7188	$1,111.72	$1,111.75	$1,111.80