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	$229.75	4.788%	$240.7504	$240.75	$240.75	$240.80
Purchase #2	$54.31	9.726%	$59.5922	$59.59	$59.60	$59.60
Purchase #3	$9.42	6.566%	$10.0385	$10.04	$10.05	$10.00
Purchase #4	$144.53	5.155%	$151.9805	$151.98	$152.00	$152.00
Purchase #5	$162.54	13.321%	$184.192	$184.19	$184.20	$184.20
Purchase #6	$223.62	6.169%	$237.4151	$237.42	$237.40	$237.40
Purchase #7	$186.75	10.598%	$206.5418	$206.54	$206.55	$206.50
7 purchase totals =	$1,010.92		$1,090.5105	$1,090.51	$1,090.55	$1,090.50