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	$57.56	3.475%	$59.5602	$59.56	$59.55	$59.60
Purchase #2	$201.81	9.581%	$221.1454	$221.15	$221.15	$221.10
Purchase #3	$98.96	7.590%	$106.4711	$106.47	$106.45	$106.50
Purchase #4	$193.53	3.564%	$200.4274	$200.43	$200.45	$200.40
Purchase #5	$234.47	5.191%	$246.6413	$246.64	$246.65	$246.60
Purchase #6	$81.28	3.200%	$83.881	$83.88	$83.90	$83.90
Purchase #7	$110.66	5.797%	$117.075	$117.08	$117.10	$117.10
7 purchase totals =	$978.27		$1,035.2014	$1,035.21	$1,035.25	$1,035.20