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	$104.69	6.403%	$111.3933	$111.39	$111.40	$111.40
Purchase #2	$96.57	8.745%	$105.015	$105.02	$105.00	$105.00
Purchase #3	$179.57	9.572%	$196.7584	$196.76	$196.75	$196.80
Purchase #4	$128.64	10.745%	$142.4624	$142.46	$142.45	$142.50
Purchase #5	$56.96	12.480%	$64.0686	$64.07	$64.05	$64.10
Purchase #6	$171.88	9.654%	$188.4733	$188.47	$188.45	$188.50
Purchase #7	$242.52	3.409%	$250.7875	$250.79	$250.80	$250.80
7 purchase totals =	$980.83		$1,058.9585	$1,058.96	$1,058.90	$1,059.10