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	$160.96	6.552%	$171.5061	$171.51	$171.50	$171.50
Purchase #2	$50.28	4.504%	$52.5446	$52.54	$52.55	$52.50
Purchase #3	$152.72	9.247%	$166.842	$166.84	$166.85	$166.80
Purchase #4	$247.66	8.658%	$269.1024	$269.10	$269.10	$269.10
Purchase #5	$114.89	8.596%	$124.7659	$124.77	$124.75	$124.80
Purchase #6	$136.40	4.727%	$142.8476	$142.85	$142.85	$142.80
Purchase #7	$167.35	8.438%	$181.471	$181.47	$181.45	$181.50
7 purchase totals =	$1,030.26		$1,109.0796	$1,109.08	$1,109.05	$1,109.00