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	$79.42	12.772%	$89.5635	$89.56	$89.55	$89.60
Purchase #2	$90.66	4.744%	$94.9609	$94.96	$94.95	$95.00
Purchase #3	$130.60	4.867%	$136.9563	$136.96	$136.95	$137.00
Purchase #4	$49.28	4.820%	$51.6553	$51.66	$51.65	$51.70
Purchase #5	$242.44	13.384%	$274.8882	$274.89	$274.90	$274.90
Purchase #6	$60.90	3.682%	$63.1423	$63.14	$63.15	$63.10
Purchase #7	$174.56	4.479%	$182.3785	$182.38	$182.40	$182.40
7 purchase totals =	$827.86		$893.5450	$893.55	$893.55	$893.70