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	$229.48	13.831%	$261.2194	$261.22	$261.20	$261.20
Purchase #2	$147.25	5.458%	$155.2869	$155.29	$155.30	$155.30
Purchase #3	$39.57	7.301%	$42.459	$42.46	$42.45	$42.50
Purchase #4	$35.95	3.448%	$37.1896	$37.19	$37.20	$37.20
Purchase #5	$100.40	13.558%	$114.0122	$114.01	$114.00	$114.00
Purchase #6	$61.58	9.649%	$67.5219	$67.52	$67.50	$67.50
Purchase #7	$198.26	10.688%	$219.45	$219.45	$219.45	$219.50
7 purchase totals =	$812.49		$897.1390	$897.14	$897.10	$897.20