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	$110.67	5.365%	$116.6074	$116.61	$116.60	$116.60
Purchase #2	$223.95	7.192%	$240.0565	$240.06	$240.05	$240.10
Purchase #3	$142.27	7.225%	$152.549	$152.55	$152.55	$152.50
Purchase #4	$244.49	12.515%	$275.0879	$275.09	$275.10	$275.10
Purchase #5	$178.37	5.280%	$187.7879	$187.79	$187.80	$187.80
Purchase #6	$150.42	10.700%	$166.5149	$166.51	$166.50	$166.50
Purchase #7	$10.41	12.305%	$11.691	$11.69	$11.70	$11.70
7 purchase totals =	$1,060.58		$1,150.2946	$1,150.30	$1,150.30	$1,150.30