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	$209.58	6.469%	$223.1377	$223.14	$223.15	$223.10
Purchase #2	$45.54	12.463%	$51.2157	$51.22	$51.20	$51.20
Purchase #3	$137.88	12.263%	$154.7882	$154.79	$154.80	$154.80
Purchase #4	$177.50	10.598%	$196.3115	$196.31	$196.30	$196.30
Purchase #5	$127.70	7.826%	$137.6938	$137.69	$137.70	$137.70
Purchase #6	$114.72	5.819%	$121.3956	$121.40	$121.40	$121.40
Purchase #7	$204.29	9.552%	$223.8038	$223.80	$223.80	$223.80
7 purchase totals =	$1,017.21		$1,108.3463	$1,108.35	$1,108.35	$1,108.30