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	$38.65	12.271%	$43.3927	$43.39	$43.40	$43.40
Purchase #2	$110.46	7.740%	$119.0096	$119.01	$119.00	$119.00
Purchase #3	$151.45	3.147%	$156.2161	$156.22	$156.20	$156.20
Purchase #4	$236.90	7.118%	$253.7625	$253.76	$253.75	$253.80
Purchase #5	$221.58	13.486%	$251.4623	$251.46	$251.45	$251.50
Purchase #6	$163.89	11.554%	$182.8259	$182.83	$182.85	$182.80
Purchase #7	$147.92	11.414%	$164.8036	$164.80	$164.80	$164.80
7 purchase totals =	$1,070.85		$1,171.4727	$1,171.47	$1,171.45	$1,171.50