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	$62.68	11.353%	$69.7961	$69.80	$69.80	$69.80
Purchase #2	$82.75	9.238%	$90.3944	$90.39	$90.40	$90.40
Purchase #3	$131.98	3.651%	$136.7986	$136.80	$136.80	$136.80
Purchase #4	$158.44	3.824%	$164.4987	$164.50	$164.50	$164.50
Purchase #5	$89.37	11.315%	$99.4822	$99.48	$99.50	$99.50
Purchase #6	$198.46	7.744%	$213.8287	$213.83	$213.85	$213.80
Purchase #7	$202.94	9.263%	$221.7383	$221.74	$221.75	$221.70
7 purchase totals =	$926.62		$996.5370	$996.54	$996.60	$996.50