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	$111.27	10.804%	$123.2916	$123.29	$123.30	$123.30
Purchase #2	$97.34	12.253%	$109.2671	$109.27	$109.25	$109.30
Purchase #3	$202.61	3.782%	$210.2727	$210.27	$210.25	$210.30
Purchase #4	$223.95	5.384%	$236.0075	$236.01	$236.00	$236.00
Purchase #5	$99.90	10.408%	$110.2976	$110.30	$110.30	$110.30
Purchase #6	$233.93	12.483%	$263.1315	$263.13	$263.15	$263.10
Purchase #7	$227.58	10.442%	$251.3439	$251.34	$251.35	$251.30
7 purchase totals =	$1,196.58		$1,303.6119	$1,303.61	$1,303.60	$1,303.60