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	$173.38	5.132%	$182.2779	$182.28	$182.30	$182.30
Purchase #2	$171.97	7.469%	$184.8144	$184.81	$184.80	$184.80
Purchase #3	$96.76	8.111%	$104.6082	$104.61	$104.60	$104.60
Purchase #4	$123.61	3.465%	$127.8931	$127.89	$127.90	$127.90
Purchase #5	$115.94	6.399%	$123.359	$123.36	$123.35	$123.40
Purchase #6	$200.69	8.399%	$217.546	$217.55	$217.55	$217.50
Purchase #7	$39.73	9.518%	$43.5115	$43.51	$43.50	$43.50
7 purchase totals =	$922.08		$984.0101	$984.01	$984.00	$984.00