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	$150.49	11.668%	$168.0492	$168.05	$168.05	$168.00
Purchase #2	$170.70	12.333%	$191.7524	$191.75	$191.75	$191.80
Purchase #3	$96.77	5.233%	$101.834	$101.83	$101.85	$101.80
Purchase #4	$60.89	11.480%	$67.8802	$67.88	$67.90	$67.90
Purchase #5	$171.25	13.768%	$194.8277	$194.83	$194.85	$194.80
Purchase #6	$65.40	5.574%	$69.0454	$69.05	$69.05	$69.00
Purchase #7	$128.48	12.425%	$144.4436	$144.44	$144.45	$144.40
7 purchase totals =	$843.98		$937.8325	$937.83	$937.90	$937.70