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	$248.73	7.591%	$267.6111	$267.61	$267.60	$267.60
Purchase #2	$129.37	9.413%	$141.5476	$141.55	$141.55	$141.50
Purchase #3	$163.40	12.653%	$184.075	$184.08	$184.10	$184.10
Purchase #4	$59.42	5.222%	$62.5229	$62.52	$62.50	$62.50
Purchase #5	$208.77	7.172%	$223.743	$223.74	$223.75	$223.70
Purchase #6	$38.57	5.641%	$40.7457	$40.75	$40.75	$40.70
Purchase #7	$82.67	4.104%	$86.0628	$86.06	$86.05	$86.10
7 purchase totals =	$930.93		$1,006.3081	$1,006.31	$1,006.30	$1,006.20