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	$59.29	5.220%	$62.3849	$62.38	$62.40	$62.40
Purchase #2	$206.55	11.518%	$230.3404	$230.34	$230.35	$230.30
Purchase #3	$87.87	13.323%	$99.5769	$99.58	$99.60	$99.60
Purchase #4	$154.94	3.299%	$160.0515	$160.05	$160.05	$160.10
Purchase #5	$218.61	11.532%	$243.8201	$243.82	$243.80	$243.80
Purchase #6	$141.92	6.220%	$150.7474	$150.75	$150.75	$150.70
Purchase #7	$144.70	8.124%	$156.4554	$156.46	$156.45	$156.50
7 purchase totals =	$1,013.88		$1,103.3766	$1,103.38	$1,103.40	$1,103.40