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	$108.32	8.715%	$117.7601	$117.76	$117.75	$117.80
Purchase #2	$179.66	8.322%	$194.6113	$194.61	$194.60	$194.60
Purchase #3	$168.82	3.261%	$174.3252	$174.33	$174.35	$174.30
Purchase #4	$202.57	10.192%	$223.2159	$223.22	$223.20	$223.20
Purchase #5	$102.27	5.392%	$107.7844	$107.78	$107.80	$107.80
Purchase #6	$178.57	3.840%	$185.4271	$185.43	$185.45	$185.40
Purchase #7	$81.67	9.767%	$89.6467	$89.65	$89.65	$89.60
7 purchase totals =	$1,021.88		$1,092.7707	$1,092.78	$1,092.80	$1,092.70