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	$79.88	3.362%	$82.5656	$82.57	$82.55	$82.60
Purchase #2	$201.98	3.229%	$208.5019	$208.50	$208.50	$208.50
Purchase #3	$174.75	12.196%	$196.0625	$196.06	$196.05	$196.10
Purchase #4	$41.29	7.300%	$44.3042	$44.30	$44.30	$44.30
Purchase #5	$178.50	12.139%	$200.1681	$200.17	$200.15	$200.20
Purchase #6	$217.38	6.566%	$231.6532	$231.65	$231.65	$231.70
Purchase #7	$54.33	5.704%	$57.429	$57.43	$57.45	$57.40
7 purchase totals =	$948.11		$1,020.6845	$1,020.68	$1,020.65	$1,020.80