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	$78.77	13.449%	$89.3638	$89.36	$89.35	$89.40
Purchase #2	$6.50	12.782%	$7.3308	$7.33	$7.35	$7.30
Purchase #3	$218.46	10.312%	$240.9876	$240.99	$241.00	$241.00
Purchase #4	$79.32	5.153%	$83.4074	$83.41	$83.40	$83.40
Purchase #5	$190.60	6.625%	$203.2273	$203.23	$203.25	$203.20
Purchase #6	$193.92	8.179%	$209.7807	$209.78	$209.80	$209.80
Purchase #7	$207.77	9.586%	$227.6868	$227.69	$227.70	$227.70
7 purchase totals =	$975.34		$1,061.7844	$1,061.79	$1,061.85	$1,061.80