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	$84.59	9.381%	$92.5254	$92.53	$92.55	$92.50
Purchase #2	$106.54	6.647%	$113.6217	$113.62	$113.60	$113.60
Purchase #3	$231.29	10.501%	$255.5778	$255.58	$255.60	$255.60
Purchase #4	$230.25	9.357%	$251.7945	$251.79	$251.80	$251.80
Purchase #5	$64.51	4.707%	$67.5465	$67.55	$67.55	$67.50
Purchase #6	$169.46	6.411%	$180.3241	$180.32	$180.30	$180.30
Purchase #7	$215.42	3.686%	$223.3604	$223.36	$223.35	$223.40
7 purchase totals =	$1,102.06		$1,184.7504	$1,184.75	$1,184.75	$1,184.70