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	$108.27	10.686%	$119.8397	$119.84	$119.85	$119.80
Purchase #2	$90.32	8.479%	$97.9782	$97.98	$98.00	$98.00
Purchase #3	$59.36	3.569%	$61.4786	$61.48	$61.50	$61.50
Purchase #4	$228.88	12.838%	$258.2636	$258.26	$258.25	$258.30
Purchase #5	$55.64	13.514%	$63.1592	$63.16	$63.15	$63.20
Purchase #6	$137.97	13.368%	$156.4138	$156.41	$156.40	$156.40
Purchase #7	$63.83	13.459%	$72.4209	$72.42	$72.40	$72.40
7 purchase totals =	$744.27		$829.5540	$829.55	$829.55	$829.60