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	$57.49	9.230%	$62.7963	$62.80	$62.80	$62.80
Purchase #2	$225.41	4.865%	$236.3762	$236.38	$236.40	$236.40
Purchase #3	$80.55	12.836%	$90.8894	$90.89	$90.90	$90.90
Purchase #4	$144.36	5.468%	$152.2536	$152.25	$152.25	$152.30
Purchase #5	$75.80	10.535%	$83.7855	$83.79	$83.80	$83.80
Purchase #6	$143.94	5.607%	$152.0107	$152.01	$152.00	$152.00
Purchase #7	$162.87	11.300%	$181.2743	$181.27	$181.25	$181.30
7 purchase totals =	$890.42		$959.3860	$959.39	$959.40	$959.50