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	$179.43	11.781%	$200.5686	$200.57	$200.55	$200.60
Purchase #2	$152.80	12.123%	$171.3239	$171.32	$171.30	$171.30
Purchase #3	$162.28	11.397%	$180.7751	$180.78	$180.80	$180.80
Purchase #4	$190.55	6.803%	$203.5131	$203.51	$203.50	$203.50
Purchase #5	$241.98	5.782%	$255.9713	$255.97	$255.95	$256.00
Purchase #6	$136.92	11.483%	$152.6425	$152.64	$152.65	$152.60
Purchase #7	$183.65	3.517%	$190.109	$190.11	$190.10	$190.10
7 purchase totals =	$1,247.61		$1,354.9035	$1,354.90	$1,354.85	$1,354.90