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	$232.49	4.140%	$242.1151	$242.12	$242.10	$242.10
Purchase #2	$85.40	7.346%	$91.6735	$91.67	$91.65	$91.70
Purchase #3	$244.90	5.131%	$257.4658	$257.47	$257.45	$257.50
Purchase #4	$61.60	9.420%	$67.4027	$67.40	$67.40	$67.40
Purchase #5	$216.55	4.789%	$226.9206	$226.92	$226.90	$226.90
Purchase #6	$194.76	8.230%	$210.7887	$210.79	$210.80	$210.80
Purchase #7	$40.86	12.437%	$45.9418	$45.94	$45.95	$45.90
7 purchase totals =	$1,076.56		$1,142.3082	$1,142.31	$1,142.25	$1,142.30