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	$13.59	6.575%	$14.4835	$14.48	$14.50	$14.50
Purchase #2	$85.37	6.450%	$90.8764	$90.88	$90.90	$90.90
Purchase #3	$171.74	4.346%	$179.2038	$179.20	$179.20	$179.20
Purchase #4	$89.63	7.458%	$96.3146	$96.31	$96.30	$96.30
Purchase #5	$238.63	8.266%	$258.3552	$258.36	$258.35	$258.40
Purchase #6	$174.97	3.283%	$180.7143	$180.71	$180.70	$180.70
Purchase #7	$245.75	11.338%	$273.6131	$273.61	$273.60	$273.60
7 purchase totals =	$1,019.68		$1,093.5609	$1,093.55	$1,093.55	$1,093.60