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	$231.35	11.634%	$258.2653	$258.27	$258.25	$258.30
Purchase #2	$61.70	4.388%	$64.4074	$64.41	$64.40	$64.40
Purchase #3	$74.52	11.240%	$82.896	$82.90	$82.90	$82.90
Purchase #4	$162.82	3.665%	$168.7874	$168.79	$168.80	$168.80
Purchase #5	$189.63	8.840%	$206.3933	$206.39	$206.40	$206.40
Purchase #6	$111.53	3.165%	$115.0599	$115.06	$115.05	$115.10
Purchase #7	$175.89	11.493%	$196.105	$196.11	$196.10	$196.10
7 purchase totals =	$1,007.44		$1,091.9143	$1,091.93	$1,091.90	$1,092.00