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	$89.79	4.474%	$93.8072	$93.81	$93.80	$93.80
Purchase #2	$78.42	4.339%	$81.8226	$81.82	$81.80	$81.80
Purchase #3	$236.42	9.170%	$258.0997	$258.10	$258.10	$258.10
Purchase #4	$60.56	3.256%	$62.5318	$62.53	$62.55	$62.50
Purchase #5	$182.64	9.176%	$199.399	$199.40	$199.40	$199.40
Purchase #6	$156.65	3.711%	$162.4633	$162.46	$162.45	$162.50
Purchase #7	$235.50	7.776%	$253.8125	$253.81	$253.80	$253.80
7 purchase totals =	$1,039.98		$1,111.9361	$1,111.93	$1,111.90	$1,111.90