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	$164.34	9.187%	$179.4379	$179.44	$179.45	$179.40
Purchase #2	$55.52	6.274%	$59.0033	$59.00	$59.00	$59.00
Purchase #3	$186.54	9.867%	$204.9459	$204.95	$204.95	$204.90
Purchase #4	$160.89	12.217%	$180.5459	$180.55	$180.55	$180.50
Purchase #5	$77.59	6.732%	$82.8134	$82.81	$82.80	$82.80
Purchase #6	$136.91	10.859%	$151.7771	$151.78	$151.80	$151.80
Purchase #7	$79.49	7.798%	$85.6886	$85.69	$85.70	$85.70
7 purchase totals =	$861.28		$944.2121	$944.22	$944.25	$944.10