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	$161.88	3.635%	$167.7643	$167.76	$167.75	$167.80
Purchase #2	$94.55	5.713%	$99.9516	$99.95	$99.95	$100.00
Purchase #3	$81.64	10.112%	$89.8954	$89.90	$89.90	$89.90
Purchase #4	$115.84	3.220%	$119.57	$119.57	$119.55	$119.60
Purchase #5	$212.59	7.232%	$227.9645	$227.96	$227.95	$228.00
Purchase #6	$194.55	6.790%	$207.7599	$207.76	$207.75	$207.80
Purchase #7	$128.47	10.462%	$141.9105	$141.91	$141.90	$141.90
7 purchase totals =	$989.52		$1,054.8162	$1,054.81	$1,054.75	$1,055.00