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	$117.87	12.432%	$132.5236	$132.52	$132.50	$132.50
Purchase #2	$215.47	12.590%	$242.5977	$242.60	$242.60	$242.60
Purchase #3	$45.96	11.574%	$51.2794	$51.28	$51.30	$51.30
Purchase #4	$96.48	13.591%	$109.5926	$109.59	$109.60	$109.60
Purchase #5	$89.57	8.526%	$97.2067	$97.21	$97.20	$97.20
Purchase #6	$245.61	7.113%	$263.0802	$263.08	$263.10	$263.10
Purchase #7	$146.73	5.860%	$155.3284	$155.33	$155.35	$155.30
7 purchase totals =	$957.69		$1,051.6086	$1,051.61	$1,051.65	$1,051.60