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	$161.96	11.501%	$180.587	$180.59	$180.60	$180.60
Purchase #2	$167.54	10.575%	$185.2574	$185.26	$185.25	$185.30
Purchase #3	$213.68	9.124%	$233.1762	$233.18	$233.20	$233.20
Purchase #4	$59.94	5.492%	$63.2319	$63.23	$63.25	$63.20
Purchase #5	$92.78	3.819%	$96.3233	$96.32	$96.30	$96.30
Purchase #6	$71.48	10.360%	$78.8853	$78.89	$78.90	$78.90
Purchase #7	$7.39	13.677%	$8.4007	$8.40	$8.40	$8.40
7 purchase totals =	$774.77		$845.8618	$845.87	$845.90	$845.90