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	$186.88	7.273%	$200.4718	$200.47	$200.45	$200.50
Purchase #2	$55.25	4.787%	$57.8948	$57.89	$57.90	$57.90
Purchase #3	$60.87	11.576%	$67.9163	$67.92	$67.90	$67.90
Purchase #4	$202.71	9.159%	$221.2762	$221.28	$221.30	$221.30
Purchase #5	$70.45	8.387%	$76.3586	$76.36	$76.35	$76.40
Purchase #6	$161.59	12.656%	$182.0408	$182.04	$182.05	$182.00
Purchase #7	$190.30	4.861%	$199.5505	$199.55	$199.55	$199.60
7 purchase totals =	$928.05		$1,005.5090	$1,005.51	$1,005.50	$1,005.60