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	$59.57	4.307%	$62.1357	$62.14	$62.15	$62.10
Purchase #2	$80.72	10.635%	$89.3046	$89.30	$89.30	$89.30
Purchase #3	$240.79	3.162%	$248.4038	$248.40	$248.40	$248.40
Purchase #4	$109.26	9.623%	$119.7741	$119.77	$119.75	$119.80
Purchase #5	$233.70	6.241%	$248.2852	$248.29	$248.30	$248.30
Purchase #6	$208.53	6.359%	$221.7904	$221.79	$221.80	$221.80
Purchase #7	$13.78	9.797%	$15.13	$15.13	$15.15	$15.10
7 purchase totals =	$946.35		$1,004.8238	$1,004.82	$1,004.85	$1,004.80