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	$21.33	5.279%	$22.456	$22.46	$22.45	$22.50
Purchase #2	$82.72	6.158%	$87.8139	$87.81	$87.80	$87.80
Purchase #3	$244.69	6.807%	$261.346	$261.35	$261.35	$261.30
Purchase #4	$67.95	5.144%	$71.4453	$71.45	$71.45	$71.40
Purchase #5	$123.79	5.673%	$130.8126	$130.81	$130.80	$130.80
Purchase #6	$219.51	8.846%	$238.9279	$238.93	$238.95	$238.90
Purchase #7	$105.61	6.794%	$112.7851	$112.79	$112.80	$112.80
7 purchase totals =	$865.60		$925.5868	$925.60	$925.60	$925.50