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	$162.46	10.212%	$179.0504	$179.05	$179.05	$179.10
Purchase #2	$56.62	13.836%	$64.4539	$64.45	$64.45	$64.50
Purchase #3	$98.92	3.702%	$102.582	$102.58	$102.60	$102.60
Purchase #4	$93.51	7.581%	$100.599	$100.60	$100.60	$100.60
Purchase #5	$129.87	11.267%	$144.5025	$144.50	$144.50	$144.50
Purchase #6	$249.40	10.863%	$276.4923	$276.49	$276.50	$276.50
Purchase #7	$39.94	13.119%	$45.1797	$45.18	$45.20	$45.20
7 purchase totals =	$830.72		$912.8598	$912.85	$912.90	$913.00