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	$67.85	6.840%	$72.4909	$72.49	$72.50	$72.50
Purchase #2	$224.69	4.298%	$234.3472	$234.35	$234.35	$234.30
Purchase #3	$111.40	6.551%	$118.6978	$118.70	$118.70	$118.70
Purchase #4	$76.69	7.395%	$82.3612	$82.36	$82.35	$82.40
Purchase #5	$239.88	9.120%	$261.7571	$261.76	$261.75	$261.80
Purchase #6	$194.88	9.419%	$213.2357	$213.24	$213.25	$213.20
Purchase #7	$64.53	9.203%	$70.4687	$70.47	$70.45	$70.50
7 purchase totals =	$979.92		$1,053.3586	$1,053.37	$1,053.35	$1,053.40