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	$191.27	3.755%	$198.4522	$198.45	$198.45	$198.50
Purchase #2	$231.90	9.446%	$253.8053	$253.81	$253.80	$253.80
Purchase #3	$70.58	9.460%	$77.2569	$77.26	$77.25	$77.30
Purchase #4	$120.54	8.856%	$131.215	$131.22	$131.20	$131.20
Purchase #5	$145.96	9.869%	$160.3648	$160.36	$160.35	$160.40
Purchase #6	$68.73	12.617%	$77.4017	$77.40	$77.40	$77.40
Purchase #7	$232.89	4.484%	$243.3328	$243.33	$243.35	$243.30
7 purchase totals =	$1,061.87		$1,141.8287	$1,141.83	$1,141.80	$1,141.90