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	$169.66	10.481%	$187.4421	$187.44	$187.45	$187.40
Purchase #2	$215.54	13.450%	$244.5301	$244.53	$244.55	$244.50
Purchase #3	$164.73	13.661%	$187.2338	$187.23	$187.25	$187.20
Purchase #4	$32.77	9.483%	$35.8776	$35.88	$35.90	$35.90
Purchase #5	$250.73	13.549%	$284.7014	$284.70	$284.70	$284.70
Purchase #6	$83.65	8.705%	$90.9317	$90.93	$90.95	$90.90
Purchase #7	$187.38	9.346%	$204.8925	$204.89	$204.90	$204.90
7 purchase totals =	$1,104.46		$1,235.6092	$1,235.60	$1,235.70	$1,235.50