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	$166.37	7.388%	$178.6614	$178.66	$178.65	$178.70
Purchase #2	$41.76	8.558%	$45.3338	$45.33	$45.35	$45.30
Purchase #3	$36.32	10.290%	$40.0573	$40.06	$40.05	$40.10
Purchase #4	$236.80	7.762%	$255.1804	$255.18	$255.20	$255.20
Purchase #5	$160.59	8.467%	$174.1872	$174.19	$174.20	$174.20
Purchase #6	$186.38	6.820%	$199.0911	$199.09	$199.10	$199.10
Purchase #7	$179.63	6.678%	$191.6257	$191.63	$191.65	$191.60
7 purchase totals =	$1,007.85		$1,084.1369	$1,084.14	$1,084.20	$1,084.20