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	$108.74	3.543%	$112.5927	$112.59	$112.60	$112.60
Purchase #2	$180.97	5.269%	$190.5053	$190.51	$190.50	$190.50
Purchase #3	$175.64	3.517%	$181.8173	$181.82	$181.80	$181.80
Purchase #4	$174.63	3.450%	$180.6547	$180.65	$180.65	$180.70
Purchase #5	$30.62	10.855%	$33.9438	$33.94	$33.95	$33.90
Purchase #6	$147.43	3.393%	$152.4323	$152.43	$152.45	$152.40
Purchase #7	$185.25	10.435%	$204.5808	$204.58	$204.60	$204.60
7 purchase totals =	$1,003.28		$1,056.5269	$1,056.52	$1,056.55	$1,056.50