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	$103.61	6.771%	$110.6254	$110.63	$110.65	$110.60
Purchase #2	$108.32	3.710%	$112.3387	$112.34	$112.35	$112.30
Purchase #3	$166.42	12.262%	$186.8264	$186.83	$186.85	$186.80
Purchase #4	$63.46	6.388%	$67.5138	$67.51	$67.50	$67.50
Purchase #5	$82.39	13.752%	$93.7203	$93.72	$93.70	$93.70
Purchase #6	$226.35	10.231%	$249.5079	$249.51	$249.50	$249.50
Purchase #7	$200.37	9.657%	$219.7197	$219.72	$219.70	$219.70
7 purchase totals =	$950.92		$1,040.2522	$1,040.26	$1,040.25	$1,040.10