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	$93.63	12.831%	$105.6437	$105.64	$105.65	$105.60
Purchase #2	$199.44	9.717%	$218.8196	$218.82	$218.80	$218.80
Purchase #3	$50.88	10.550%	$56.2478	$56.25	$56.25	$56.20
Purchase #4	$53.27	4.537%	$55.6869	$55.69	$55.70	$55.70
Purchase #5	$133.60	10.268%	$147.318	$147.32	$147.30	$147.30
Purchase #6	$99.31	6.210%	$105.4772	$105.48	$105.50	$105.50
Purchase #7	$219.59	7.736%	$236.5775	$236.58	$236.60	$236.60
7 purchase totals =	$849.72		$925.7707	$925.78	$925.80	$925.70