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	$90.80	3.409%	$93.8954	$93.90	$93.90	$93.90
Purchase #2	$167.33	5.476%	$176.493	$176.49	$176.50	$176.50
Purchase #3	$67.46	8.491%	$73.188	$73.19	$73.20	$73.20
Purchase #4	$81.35	3.716%	$84.373	$84.37	$84.35	$84.40
Purchase #5	$98.64	6.794%	$105.3416	$105.34	$105.35	$105.30
Purchase #6	$21.33	5.558%	$22.5155	$22.52	$22.50	$22.50
Purchase #7	$101.38	9.816%	$111.3315	$111.33	$111.35	$111.30
7 purchase totals =	$628.29		$667.1380	$667.14	$667.15	$667.10